Completed Physics Manual
-
Upload
shanmugam-ramesh -
Category
Documents
-
view
136 -
download
1
Transcript of Completed Physics Manual
Physics Laboratory Manual
Fig.1 Vernier Caliper
(a). Zero Error
(b)Positive error (c) Negative error
Adithya Institute of Technology Page 1
Physics Laboratory ManualExpt. No.Date
1. VERNIER CALIPER
Aim:
To find the breadth of a given object using vernier caliper.
Apparatus Required:
Vernier caliper and the given object.
Procedure,
A vernier attached to a movable jaw sliding on a metal scale with a fixed jaw at the
zero ends is called the vernier caliper. The upper fixed jaw and movable jaw are attached
so as the distance between their outer ends equals the distance between the inner ends of
the lower jaws. There is a stud to fix the vernier. The pointed strip at the farther end is
intended for depth measure.
(i) Determination of Least Count
Least count of a measuring instrument is the smallest length that can be
accurately measured with it. In the vernier caliper it is the difference between one main
scale division (MSD) and one vernier division (VSD). After ascertaining the value of
one main scale division, the zero of the vernier is fixed to a definite main scale division
and the distance between the first and the last vernier scale division (VSD) is found in
terms of the main scale divisions. The value of the vernier division in terms of MSD is
calculated. Then the least count is determined by the following formula:
Adithya Institute of Technology Page 2
Physics Laboratory Manual
To find the least count:
Least count = 1 MSD – 1 VSD
10 VSD coincides with 9 MSD
Therefore,
10 VSD = 9 MS
Observation
Least Count = 0.01 x10-2 m Zero Error = div
Zero Correction = x 10-2m
S.N
O
MSR
X 10-2m
VSC
Div
VSR=VSC X
L.C
X 10-2m
Observed reading
OR= MSR + VSR
X 10-2m
Correct Reading
CR=OR ± ZC)
X 10-2m
1
2
3
4
5
Mean value of breath
Adithya Institute of Technology Page 3
Physics Laboratory Manual
1 VSD = 9/10 MSD
1 MSD = 1 mm
Therefore,
LC = 1 MSD – 1 VSD
= 1 mm – 9/10 mm
= 1/10 mm
= 0.1mm or .01 cm
Usually the readings are noted in cms only.
(ii) Determination of Zero error
(a) Zero error:
When the fixed and movable jaws are brought into contact, if the zero of the
vernier coincides exactly with the zero of the main scale, then there is no zero error.
(b) Positive error:
When the two jaws are in contact, if the zero of the vernier lies right to the zero
of the main scale (i.e. in the positive direction of measurement) the error is positive. The
coinciding division of the vernier with any MSD is implied by the least count to get the
value of the error.
(1) If the yth division of vernier coincides with any one of the main scale division ,
then
Zero error = +y × LC
Zero correction = -y × LC
For example, if the fifth division of the vernier scale exactly coincides with any one of the
main scale division,
Adithya Institute of Technology Page 4
Physics Laboratory Manual
CALCULATION
Adithya Institute of Technology Page 5
Physics Laboratory Manual
If the zero of the vernier lies left to the zero of the main scale (i.e. in the
negative direction of measurement) the error is negative. The coinciding division of the
vernier with any MSD is mulplied by the least count to get the val;ue of the error.
(2) If the yth division of the vernier coincides with any one main scale division,
then , Zero error = -y × LC
Zero correction = +y × LC
For example, if the third division of the vernier scale exactly coincides with any
one of the main scale division, then Zero error = +5 × LC
Zero correction = -5 × LC
= +3 ×0.01cm
= +0.03 cm
(iii) Determination of the breadth of the given object
The given object is held between the two lower jaws of vernier caliper as in fig 1.
The main scale reading which is just preceding or exactly coinciding with the zero of vernier
scale is noted as the MSR. The vernier scale division that coincides exactly with any of the
main scale division is noted as VSD. Then, the breadth of the given object is determined by
the given formula.
Breadth of the object = [MSR + VSR]
Where VSR = VSC × LC ± ZC
The object is held in different positions and the experiment is repeated.
Result: The breadth of the given object = ……………. × 10-2m.
Adithya Institute of Technology Page 6
Physics Laboratory Manual
Fig.1. Screw Gauge
Adithya Institute of Technology Page 7
Physics Laboratory ManualExpt. No:
Date:
2. SCREW GAUGE
Aim:
To find the thickness of the given object using screw gauge.
Apparatus Required:
Screw gauge and the given object.
Procedure:
A uniformly threaded screw works in a hollow cylindrical nut, whose left end is
attached to a U-shaped frame. A scale with its division corresponding to the screw
threads engraved on the cylindrical nut is called pitch scale. A plane stud is opposite to
the plane tip of the screw. Its head is mild and to avoid over screwing a ratchet
arrangement is fixed. The beveled edge of the metal sleeve attached to the head of the
screw is divided into a definite number of divisions known as head scale.
(i) Determination of least count :
Least count is the smallest length that can be accurately measured by the
instrument. The least count is calculated by dividing the pitch by the number of divisions
on the head scale,
One Pitch scale division or Pitch
Total number of divisions on the head scale
Distance moved by the head scale on the pitch scale
No of rotations given to the head scale
One Pitch scale division = 1x10-3m
Then, Least count = 1/100 x10-2m , usually here the readings are noted in mm only.
Adithya Institute of Technology Page 8
Least Count (LC) =
Pitch =
Physics Laboratory Manual
Observation
Least Count = 0.01x10-3 m Zero Error = div
Zero Correction = x10-3m
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed
reading
OR= PSR +
HSR
X 10-3m
Correct
Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Adithya Institute of Technology Page 9
Mean
Physics Laboratory Manual
(ii) Determination of Error:
(a) Zero error:
When the top of the screw is made to contact the fixed stud, if the zero of the
head scale coincides exactly with the zero of the pitch scale on the reference line, then there
is no zero error.
(b) Positive error
If the head scale zero has not crossed the pitch scale reference line, the error is
positive. If yth division on head scale coincides with pitch scale reference line, the error is +y
divisions and zero correction is (-y ×LC).
For example, as in fig., when 5th division on head scale coincides with pitch scale
reference line, the zero error is + 5 divisions and the zero correction is -5 × LC
i.e. Zero correction = -5 × 0.01x10-3m
= -0.05x10-3m
(c) Negative error:
If the head scale zero has crossed the pitch scale reference line, error is
negative. If yth division head scale division coincides with pitch scale reference line, the
error is – (100-y) division and zero correction is + (100-y) × LC.
For example, as in fig.b, when 95th division on head scale coincides with pitch scale
reference line, the zero error is –(100-95) divisions. i.e. -5 divisions and the zero correction
is +5 × LC
Adithya Institute of Technology Page 10
Physics Laboratory Manual
i.e. Zero correction = +5 × 0.01x10-3m
= +0.05x10-3m
(iii) Determination of the thickness of a wire
The given wire is gently gripped between a fixed stud and the screw tip. The
pitch scale division just in front of the head scale and the coinciding division of the head
scale with the reference line are noted.
Head scale reading (HSR) = HSC×LC
Observed reading (OR) = PSR + HSR
Correct Reading = OR ± ZC
Calculation,
Adithya Institute of Technology Page 11
Physics Laboratory Manual
Result
Thickness of a given wire = ………………….. ×10-3m.
Adithya Institute of Technology Page 12
Physics Laboratory Manual
Fig.1.Overview of Travelling Microscope
Adithya Institute of Technology Page 13
1 VSD = cm
Physics Laboratory ManualExpt. No:
Date:
3. TRAVELLING MICROSCOPE
Aim
To find the radius of the given capillary tube.
Apparatus Required
Travelling microscope, a reading lens, capillary tube and a stand.
Procedure
The Travelling microscope consists of a compound microscope sliding along a
graduated vertical pillar. The vertical pillar is fixed to a horizontal base resting on screws.
Two screws at the base of the microscope are used for its leveling. The main scale
divisions are marked on the base and on the pillar. Vernier scale is attached to the base of
the pillar.
(i) Determination of Least count
The value of one main scale division (MSD) is 0.05 cm. The vernier scale is
divided into 50 divisions which is equivalent to 49 main scale divisions.
L.C = 1 MSD - 1 VSD
20 MSD = 1 cm
1 MSD = 1/20 cm = 0.05 x10-2m
50 VSD coincides with 49 MSD
Here 50 VSD = 49 MSD
1 49 49 1
50 50 20
1 VSD =0.049 x10-2m
Adithya Institute of Technology Page 14
MSD or
Physics Laboratory Manual
Observation
Least Count = 0.001x10-2m
Cross wire PositionMicroscope Readings Diameter
A ~ B
X 10-2m
MSR
X 10-2m
VSC
Div
TR= MSR+ (VSCx
LC) X 10-2mVertical crosswire
Left (A)
Right (B)
Horizontal
crosswire
Bottom (B)
Mean
Mean radius of the capillary tube = ………………. ×10-2 m
LC = 1 MSR - 1 VSR
= 0.05-0.049
LC = 0.001 x10-2m
Adithya Institute of Technology Page 15
Physics Laboratory Manual
(ii) Determination of radius of the Capillary tube
First the capillary tube is placed on the separate stand and the Travelling
microscope is adjusted to view the capillary tube. The microscope is focused in the inner
bore of capillary tube. The vertical cross wire is made to coincide with any one end(say left)
and by moving the head slightly while viewing, if the cross wire shifts with respect to the
focused point, then by pulling the eye piece slightly out or pushing in, adjustment is made to
avoid parallax error. Main scale and vernier scale readings (R1) are taken (a reading lens is
used to observe the vernier coincidence, carefully). Now moving the microscope in
horizontal direction, vertical cross wire is made to coincide with other end (say right) of the
inner bore of capillary tube. Main scale and vernier scale readings (R2) are taken. The
difference between these two readings gives the diameter and hence the radius of the inner
bore of the capillary tube. Then the microscope is moved vertically so that the horizontal
cross wore is made to coincide with the top end of inner bore. Corresponding main scale and
vernier scale readings (R3) are taken. Now moving the microscope in vertical direction,
horizontal cross wire is made to coincide with other end (say bottom) of the inner bore of
capillary tube. Main scale and vernier scale readings (R4) are taken. The difference between
these two readings gives the diameter and hence the radius of the inner bore of the capillary
tube.
Result:
Radius of the capillary tube = …………………… ×10-2 m
Adithya Institute of Technology Page 16
Physics Laboratory Manual
Fig.1. Spectrometer
Expt. No:
Adithya Institute of Technology Page 17
Physics Laboratory Manual
Date:
4. SPECTROMETER
Aim:
To determine the difference between vernier A and vernier B in a spectrometer.
Apparatus Required :
Spectrometer, a reading lens and a spirit level.
Description of the Instrument:
Spectrometer consists of collimator, telescope, vernier table and prism table.
Collimator consists of a brass tube with collimating lenses at one end and a vertical slit of
adjustable width at the other end. To obtain the parallel beam of light, the distance between
the slit and the lens is adjusted with the help of a side screw attached to the collimator. The
telescope is an ordinary refracting telescope with an objective lens near the collimator and an
eye piece at the other end. The telescope is fitted on one arm of the spectrometer and can be
rotated about the central axis. The prism table is made up of two circular platforms one
above the other connected together by three leveling screws. The vernier table has two
verniers, VA and VB each having main scale and vernier scale. Here one main scale division
is equal to half a degree. Each vernier scale has 30 divisions, which is equal to 29 main scale
divisions.
Preliminary Adjustments to be followed before taking measurements:(i) Eyepiece
The telescope is turned towards and focused at the white wall the the eyepiece is moved
inwards or outwards until the cross wires are clearly seen.
(ii) Telescope
The telescope is turned towards a distant object where it is adjusted for parallel rays.
The distance between the eyepiece and the objective is adjusted till a clear imagethe crowire.
Adithya Institute of Technology Page 18
Physics Laboratory Manual
Observation
LC = 1' Total reading, TR = MSR + (VSC ×LC) degrees
S. No
Position
of
telescope
Vernier A Vernier B VA ~
VB
degrees
MSR
Degrees
VSC
Div
TR
Degrees
MSR
Degrees
VSC
Div
TR
Degrees
1. Left
2. Right
Adithya Institute of Technology Page 19
Physics Laboratory Manual
(iii) Slit
The slit is made narrow with the help of the screw, provided aside of the
slit. This controls the amount of light passing through the collimator.
(iv) Collimator
The telescope is brought in line with the collimator. The slit is
illuminated by a source of light. If the image of the slit appears blurred,
then the screw of the collimator is adjusted until a clear image is seen
when viewed through the telescope. Now the rays of light emerging from
the collimator will be rendered parallel.
(v) Prism table
By releasing the clamping screw, the prism table is raised so that the table
top is in line with the base of the collimator. The prism table is made
horizontal by using the center spirit level. The spirit level is placed
perpendicular to the line joining the two screws and the bubble brought to
the center by adjusting the third screw. By keeping the spirit level at
different places the prism table is made horizontal.
Adithya Institute of Technology Page 20
1VSD =
Physics Laboratory ManualDetermination of Least count
The main scale is graduated in half degree. There are 30 divisions in the vernier.
Least count = 1MSD - 1VSD.
1 MSR = ½ degree = 30'
Total no of divisions on vernier scale = 30
30 VSD coincides with 29 MSD
30 VSD = 29 MSD
2930
1VSD = 29/30 × 30' = 29'
LC = 1MSD - 1VSD
= 30'- 29'
Least count (L.C) =
Measurement
Before doing any experiment using spectrometer, the above mentioned initial
adjustments have to be made. While performing the experiment, the main scale and vernier
scale readings are noted from both the verniers in VA and VB in degrees and minutes.
Therefore,
Total reading = MSR + (VSC ×LC) degrees
Adithya Institute of Technology Page 21
MSD
Physics Laboratory Manual
Calculation,
Result
The readings are noted and the difference between vernier A and vernier B is found to
be …………………….. Degrees.
Adithya Institute of Technology Page 22
Physics Laboratory Manual
Fig.1. Experimental set up for Particle size determination
Adithya Institute of Technology Page 23
2 1 23 34 4
Sin θm
mN
dm
D
Physics Laboratory Manual 1, 2, 3, 4 order of spectrum
Expt. No:
Date:
1. LASER EXPERIMENTS
Aim:
To determine
(i) the particle size of the lycopodium powder using semiconductor laser
(ii) the wavelength of the given laser source using grating
Apparatus Required:
Semiconductor laser, lycopodium powder coated glass slide, Slide holder Screen,
scale, grating,
Formula,
(i) The size of the particle D = 1.22mλ/Sinθ m
θ = tan-1(r/d)
where
D - Size of the particle (× 10-2m)
λ - Wavelength of the laser source (× 10-10m)
d - Distance between the particle slide and the screen. (× 10-2m)
m - Order of diffraction (No unit)
r - Radius of the nth order ring (× 10-2m)
θ - Angle of diffraction ( degrees)
(ii) Wavelength of the laser source, λ = m
where θm = tan-1 degrees
Adithya Institute of Technology Page 24
Physics Laboratory ManualObservation
(i) To determine size of the particle
Distance
between screen
and glass plate,
d,X 10-2m
Order of
diffraction
(m) (No
unit)
Radius of
mth order
ring, r
X 10-2m
Angle of
diffraction
θ=[tan -1(r / d)]
degrees
Particle size
D = 1.22mλ/Sinθ
X 10-6m
1.
2.
3.
4.
5.
Mean
Adithya Institute of Technology Page 25
Physics Laboratory Manual
Fig.2. Experimental set up for laser- wavelength determination
λ - Wavelength of the laser source (× 10-10m)
N - Number of lines per meter in the grating (lines/m)
m - Order of diffraction (No unit)
θ - Angle of diffraction (degrees)
dm – distance of the mth order spectrum from zeroth order(× 10-2m
D - Distance between grating and the screen (× 10-2m)
Adithya Institute of Technology Page 26
Physics Laboratory Manual
Fig.3 Determination of wavelength of the laser source
Adithya Institute of Technology Page 27
Physics Laboratory ManualProcedure
(i) Determination of particle size
The lycopodium powder is sprinkled on the glass plate and placed in between a laser
beam and a screen as shown in fig 1. A diffraction pattern is obtained as shown in fig.2. The
distance between the glass plate and the screen is adjusted to get the clear and more number
of orders of the fringes. By measuring the radius(r) of the first order circle and the distance
between the screen and slide (d), the particle size (D) can be calculated using the given
equation relating to the radius of the circle and the angle of diffraction corresponding to the
mth ring.
(ii) Determination of wavelength of the laser source
The grating is kept between laser light and the screen as shown in fig 2. Laser
beam gets diffracted by the grating. Diffraction pattern of several orders is formed on the
screen. The distance between the screen and the grating D is measured. The distance (d)
between the zero order and first order is measured. Experiment is repeated for different
values of D and d. using the formula λ is measured. Readings are tabulated.
S.No Distance between screen
and grat-ing, D×10-2m
Order of diffraction
m
(No unit)
Distance between zeroth
order and mth order (d)×10-2m
Angle of dif-fraction
ө=tan-1(d/D)
degrees
Wavelengthλ = [sin θ/
Nm]m
×10-10mLeft Right Mean
Adithya Institute of Technology Page 28
Physics Laboratory Manual
Mean λ
(ii) DETERMINATION OF WAVELENGTH OF THE LASER SOURCE:
Calaulation,
Adithya Institute of Technology Page 29
Physics Laboratory Manual
Adithya Institute of Technology Page 30
Physics Laboratory Manual
Adithya Institute of Technology Page 31
Physics Laboratory Manual
Result
1. The grain size of the lycopodium powder =……………….. m
2. The wavelength of the given laser source =……………….. (×10-10m)
Adithya Institute of Technology Page 32
Physics Laboratory Manual
Fig.1. Air Wedge Arrangement
Adithya Institute of Technology Page 33
λl2
Physics Laboratory Manual Fig.2. Interference- fringe pattern
Expt. No:
Date:
2. AIR WEDGE-THICKNESS OF A THIN WIRE
Aim:
To find the thickness of a thin wire by forming interference fringes using air-wedge
arrangement.
Apparatus Required:
Two optically plane rectangular glass plates, thin wire, Travelling microscope,
Sodium vapour lamp etc.,
Formula,
Thickness of the thin wire ,
t = m
Where ,
- Wavelength of Sodium vapour lamp (5893 ×10-10m)
- Bandwidth (distance between any two dark or bright frings) (×10-2m)
l - Distance between the edge of contact and the wire( length of the air wedge)
(×10-2m)
Adithya Institute of Technology Page 34
Physics Laboratory Manual
Determination of band width () using Traveling Microscope:
S.NoOrder of the
fringesMicroscope Reading Bandwidth of
10 fringesBandwidth of one fringe x 10-2 m
MSRx 10-2 m
VSC DIV
TRx 10-2 m
Mean bandwidth = x 10-2 m
Calculation,
Adithya Institute of Technology Page 35
Physics Laboratory Manual
Principle
When a normally reflected monochromatic light falls on a wedge shaped air film and
if viewed through a microscope, alternate dark and bright interference bands of equal
thickness are observed.
Procedure
Two optically plane glass plates are tied together at one end .At the other end a thin
wire is introduced with its length perpendicular to the length of the plate. The plates are tied
together at this end also. A thin air wedge of steadily increasing thickness is formed between
the plates. Light from Sodium vapour lamp is rendered parallel by a convex lens and made
to fall on the glass plate kept inclined at angle of 45 to the horizontal. The partially
reflected light travels vertically downwards and it is incident normally on the air wedge. An
interference pattern consisting of a number of alternate dark and bright bands will be
obtained. This is viewed by the Travelling microscope arranged above the glass plates. The
first well-defined dark band near the left end is taken as the n th Band. The microscope is
adjusted such that its vertical cross wire is coinciding with the n th band. The reading on the
horizontal scale of the microscope is noted. Cross wire is made to coincide with successive
fifth fringes and the corresponding microscope readings are noted. The readings are to be
taken up to fifty fringes. From these readings, the mean fringe width () is found. The
distance ‘l’ is measured with the help of the Travelling microscope and by using the given
formula thickness of the thin wire is calculated.
Result
Adithya Institute of Technology Page 36
Physics Laboratory Manual Thickness of the given thin wire =…………………………m.
Adithya Institute of Technology Page 37
Physics Laboratory Manual
Fig.1.Ultrasonic interferometer
Expt. No:
Date:
3. ULTRASONIC INTERFEROMETER –VELOCITY OF
ULTRASONIC WAVES AND COMPRESSIBILITY OF LIQUID
Adithya Institute of Technology Page 38
2d x
1 V2
ρ
Physics Laboratory Manual
Aim:
(i) To determine the velocity of ultrasonic waves in the given liquid using
Ultrasonic interferometer.
(ii) To determine the compressibility of the given liquid.
Apparatus required:
Ultrasonic interferometer, Measuring cell, Frequency generator, liquid, etc,
Formula,
(i) Velocity of Ultrasonic waves in the given liquid v = nλ ms-1
Where λ = m
(ii)Compressibility of the given liquid k = ρ m2N-1
λ - Wavelength of Ultrasonics (m)
n - Frequency of the generator which excites the crystal (Hertz)
d - Distance moved by the micrometer screw (m)
x - Number of oscillations (No unit)
ρ – Density of the given liquid (kgm-3)
(i) To determine the velocity of ultrasonic waves Frequency= Hz
S.NoMicrometer Readings Distance
for maximum Current(d)
𝜆 = 2d/ x
X 10-3mPSR
X 10-3mHSCDiv
TR= PSR+(HSCx LC) X 10-3m
V= nλ
Adithya Institute of Technology Page 39
Physics Laboratory Manual X 10-3m
Mean ( 𝜆) = X 10-3m
Theory
An Ultrasonic Interferometer is a simple and direct device to determine the velocity of
ultrasonic waves in liquid with a high degree of accuracy. Here the high frequency generator
generates variable frequency, which excites quartz crystal placed at the bottom of the
measuring cell. The excited quartz crystal generates ultrasonic waves in the experimental
Adithya Institute of Technology Page 40
Physics Laboratory Manualliquid. The liquid will now serve as an acoustical grating element. Hence when ultrasonic
waves pass through the rulings of grating, successive maxima and minima occur, satisfying
the condition for diffraction. In high frequency generator two knobs are provided for initial
adjustments. One is marked with "Adj" (set) and the other with "Gain" (sensitivity). With
knob marked "Adj" the position of the needle on the ammeter is adjusted and with the knob
marked "Gain", the sensitivity of the instrument can be increased for greater deflection, if
desired.
Procedure
The electrodes are connected to the output terminal of the frequency generator
through a shielded cable. The cell is filled with the experimental liquid before switching ON
the generator. Now, when the frequency generator is switched ON, the Ultrasonic waves
move normal from the Quartz crystal till they are reflected back by the movable reflector
plate. Hence, standing waves are formed in the liquid in between the reflector plate and the
Quartz crystal. The distance between the reflector and crystal is varied using the micrometer
screw such that the anode current of the generator increases to a maximum and then
decreases to a minimum and again increases to a maximum. The distance of separation
between two successive maximum or two successive minimum in the anode current is equal
to half the wavelength of the Ultrasonic waves in the liquid. Therefore, by noting the initial
and final position of the micrometer screw for one complete oscillation (maxima- minima-
maxima) the distance moved by the reflector can be determined.
Calculation,
Adithya Institute of Technology Page 41
Physics Laboratory Manual
To minimize the error, the distance (d) moved by the micrometer screw is noted for 'x'
number of oscillations (successive maxima), by noting the initial and final reading in the
micrometer screw and is tabulated. From the total distance (d) moved by the micrometer
screw and the number of oscillations (x), the wavelength of ultrasonic waves can be
Adithya Institute of Technology Page 42
Physics Laboratory Manualdetermined using the formula f... = 2d / x. From the value of f... and by noting the frequency
of the generator (n), the velocity of the Ultrasonic waves can be calculated using the given
formula. (1) After determining the velocity of the Ultrasonic waves in liquid, the
compressibility of the liquid is calculated using the given formula. (2)
Result
(i) The velocity of Ultrasonic waves in the given liquid = ms-1
(ii) Compressibility of the given liquid = m2N-1
Adithya Institute of Technology Page 43
Physics Laboratory Manual
SPECTROMETER
Expt. No:
Adithya Institute of Technology Page 44
sinө mλ
sinө mN
Physics Laboratory ManualDate:
4. SPECTROMETER – WAVELENGTH OF MERCURY SOURCE USING
GRATING
Aim:
(i) To determine the number of lines per meter on the grating
(ii) To find the wavelength of the prominent spectral lines in the mercury source.
Apparatus Required:
Spectrometer, Plane transmission grating, Mercury vapour lamp, Reading lens etc.,
Formula,
(i) Number of lines per meter on the grating,
N = lines/m
(iii) Wavelength of a spectral line, λ = Ǻ
where
- Angle of diffraction (degree)
m - Order of diffraction (No unit)
Procedure
(i) Adjustment of the grating for Normal Incidence
Preliminary adjustments of the spectrometer are made. The grating is mounted
on the grating table with its ruled surface facing the collimator. The slit is illuminated by a
source of light (either sodium or mercury vapour lamp) and is made to coincide with the
vertical cross wire. The vernier scales are adjusted to read 0 deg and 180 deg for the direct
ray (fig .1). The telescope is rotated through an angle of 90 deg and is fixed (fig 2). The
Observation
Adithya Institute of Technology Page 45
sinө mλ
Physics Laboratory Manual(i) To determine the number of lines per meter of the grating
λ =
S.
No
Telescope readings
(degrees)Difference2θ (deg) Mean
2θ
(deg)
Meanangle
θ
N=
×105
lines /mLeft Right
A1 B2 A1 B2 A(A1-A2)
B(B1-B2)
grating table is adjusted until the image coincides with the vertical cross wire. Both the
Adithya Institute of Technology Page 46
sinө mλ
Physics Laboratory Manualgrating table and the telescope is fixed at this position (fig.3). Now rotate the vernier table
through 45 deg in the same direction in which the telescope has been previously rotated. The
light from the collimator incidents normally( perpendicularly) on the grating. The telescope
is released and is brought in line with the direct image of the slit. Now the grating is said to
be in Normal incidence position (fig. 4)
(ii) Determination of Number of lines per metre of the grating:
The slit is illuminated by mercury green of known wavelength. The telescope is
released to catch the diffracted image of the first order on the left side of the central direct
image. The readings in the two verniers are noted. It is then rotated to the right side to catch
the diffracted image of the first order, the corresponding readings are noted. The difference
between the positions of the right and left sides gives twice the angle of diffraction 2.
For a first order spectrum m = 1 and for green line , λ = 5461Ǻ,
The number of lines per metre on the grating (N) is calculated using the formula
N = lines/m
(iii) Determination of wavelength of prominent spectral lines of the mercury
spectrum
The grating for normal incidence is not disturbed. The telescope is brought round on
both sides of the direct image to view the first order spectrum. The vertical cross wire of the
telescope is made to coincide successively with each one of the prominent lines and the
readings are taken. Similarly the corresponding readings of the same prominent lines for the
CALCULATION
Adithya Institute of Technology Page 47
Physics Laboratory Manual
first order on the other side are taken. The observations are tabulated. The angle of
Adithya Institute of Technology Page 48
sinө mN
Physics Laboratory Manualdiffraction for each prominent line is determined as before.
The wavelength of the lines of the mercury source is calculated using the formula.,
λ = Ǻ
Result
(i) The number of lines per meter on the grating = ………………. lines /m.
(ii) The wavelengths of the different spectral lines of the mercury spectrum are
λV = ………… Ǻ λY1 = ……………. Ǻ
λB = ………… Ǻ λY2 = ……………. Ǻ
λBG = ………….Ǻ λR1 = ……………. Ǻ
λG = ………… Ǻ λR2 = ……………. Ǻ
Adithya Institute of Technology Page 49
Physics Laboratory ManualFig. 1 Lee's Disc Apparatus
Adithya Institute of Technology Page 50
MSRd(r+2h)
πr2(2r+2h)(θ1 - θ2 )
dθ
dt
Physics Laboratory ManualExpt. No:
Date:
5.LEES DISC-CO-EFFICIENT OF THERMAL CONDUCTIVITY OF
A BAD CONDUCTOR
Aim:
To determine the thermal conductivity of a bad conductor such as cardboard or
glass using lee’s disc apparatus.
Apparatus required:
Lee’s disc apparatus, card board, thermometer, Stop watch, Vernier caliper,
Screw gauge, Steam boiler, etc,
Formula,
The co-efficient of Thermal conductivity
K = W/mK
M- Mass of the brass disc (×10-3 kg)
S- specific heat of the material of the disc( J /Kg/K)
R = - Rate of cooling at steady state temperature θ2 (°C/sec) (from graph)
dθ – Change in temperature (°C)
dt – Change in time (sec)
d- Thickness of the bad conductor (×10-3 m)
r- Radius of the metallic disc or cardboard (×10-2 m)
h- Thickness of the metallic disc (×10-3 m)
θ1-Temperature of the steam in ºC
θ2- Steady temperature of the metallic disc in ºC
(i) To find the thickness of the brass disc (h)
Adithya Institute of Technology Page 51
Mean
Physics Laboratory ManualZE = div
LC = 0.01X10-3m ZC = x10-3m
S.NOPSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Principle
Adithya Institute of Technology Page 52
Physics Laboratory Manual The Principle involved in the Lee’s disc is conduction of heat. In steady state the
temperature of the lower metal plate becomes constant and heat is lost by the metal disc and
heat is gained by the bad conductor.
Procedure: Lee’s disc consists of thick brass disc A suspended horizontally by strings
from a metal ring attached to a retort stand. The cardboard disc of the same diameter is
placed on the brass disc. A steam chamber B of the same cross section as the brass disc is
placed on the cardboard. The thermometers T1 and T2 are inserted into the both discs A and
B to record the temperature on the two sides of the cardboard.
The main thickness of the cardboard disc is determined using screw gauge. The
radius r of the lower metallic disc A is found using vernier calipers. The mass M of the
lower metallic disc is also found with the help of weighing balance. Steam is allowed to pass
through the steam chamber. Heat is conducted through the cardboard to the metal disc A.
The thermometers indicate rise of temperature.
(a) Static part: Determination of steady state temperature θ1 and θ2
Steam is passed through the steam chamber for a sufficiently longtime until
thermometers T1 and T2 indicate steady temperatures θ1 and θ2 respectively. When the
temperatures of thermometers T1 and T2 remain steady it means that the whole arrangement
has reached steady state. In this state heat is conducted into the lower slab through the
cardboard disc, is just equal to the heat radiated by the flat bottom of the lower slab.
(b) Dynamic part: Determination of Rate of cooling (R) of the brass disc
After noting the steady temperature θ2°C, The cardboard disc is now removed
and A is heated in direct contact with the steam chamber B until its temperature rises by
above 10º above the steady temperature θ2. Now the slab A is suspended separately and
allowed to cool. When its temperature reaches (θ2+5)º a stop clock is started and the time is
(ii) To find the thickness of the card board (d)
ZE = div
Adithya Institute of Technology Page 53
dθ dt
ABBC
Physics Laboratory Manual LC = 0.01x10-3m ZC = x10-3m
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Model graph
R- By graphical method
R = ,
dθ = (θ2 +0.5)-( θ2-0.5) = 1
dt = BC
recorded for every 1 degree fall of temperature until its temperature reaches (θ2-5)º. A graph
Adithya Institute of Technology Page 54
Mean
Physics Laboratory Manualis drawn taking time along the x axis and temperature along the y axis. By drawing a tangent
to the graph at the temperature θ2, the corresponding rate of fall of temperature R of the brass
disc A can be found.
(iv) To find rate of cooling (R) by experiment
Calculations
Mass of the brass disc A M = 850× 10-3 Kg
Radius of the brass (card board) disc r = ................... × 10-2 m
Thickness of the brass disc h =................. × 10-3 m
Thickness of the bad conductord = ............... × 10-3 m
Specific heat capacity of brass disc S = 370 J/Kg/K
Steady temperature of the steam chamber,θ1 = ................ °C
Steady temperature of brass disc θ2= ................ °C
Rate of fall of temperature R = .................. °C/ sec
Variation of temperature with te : (Rate of cooling)
Adithya Institute of Technology Page 55
Physics Laboratory ManualTemperature
°C Time
Second
Calculation,
Adithya Institute of Technology Page 56
Physics Laboratory Manual
Result
Thermal conductivity of the given bad conductor K = .........................W/mK
Adithya Institute of Technology Page 57
Physics Laboratory Manual
Fig. 1. Hysteresis circuit diagram
Adithya Institute of Technology Page 58
DATE:
EX:
(i tan θ).x.y.n.Be(d2 + L2)2
r2LD
Physics Laboratory Manual
6. HYSTERESIS LOSS IN A FERROMAGNETIC MATERIAL
Aim:
To find the hysteresis loss or energy loss per unit volume per cycle of magnetization
of a ferromagnetic substance.
Apparatus Required :
Ferromagnetic uniform rod, Batteries, Ammeter, Key, Commutator , Rheostat,
Solenoid, Compensating coil, Deflection magnetometer, Screw gauge.
Formula:
Intensity of magnetization is given by
I = J/m2/cycle
Where,
i tan θ- Area of the hysteresis loop(m3)
x and y – Scale factors on x and y axes
n - Number of turns per metre in the solenoid
Be- Horizontal component of the earth’s magnetic field (40×104 Tesla)
θ – Deflection in the magnetometer (degrees)
r – Radius of the ferromagnetic rod (×10-3 m)
d – Distance between the rod and centre of compass box (×10-2 m)
L – Length of the ferromagnetic rod (×10-2 m)
Adithya Institute of Technology Page 59
Physics Laboratory Manual
Fig.2.Hysteresis loop
Principle.
From the magnetic effects of currents, we can also prove that, when a current (I) ampere
Adithya Institute of Technology Page 60
Physics Laboratory Manualpasses through the solenoid, the magnetising field (H) will be given by
H = μ0 n I
where
μo - Permeability of vacuum ( 4 π x 10-7 henry/metre. )
n - Number of turns/ metre in the solenoid
The energy loss per cycle of magnetization per unit volume of the specimen is given by the
area of I - H curve.
Procedure
Now the ferromagnetic rod is placed inside the solenoid along its axis such that
the two ends of the rod are equidistant from the two ends of the solenoid and bottom end is
in the plane of the magnetic needle of the compass box. Now the circuit is switched on and
rheostat adjusted for maximum current (say 5 amps). There will be deflection in the compass
box. (This need not to be recorded.) Then, slowly the The hysteresis apparatus containing
solenoid and deflection magnetometer is first set in Tan A position. The compass box is
adjusted such that the aluminium pointer reads 0-0. Then the circuit connections are made as
shown in figure without the ferromagnetic rod inside the solenoid. A deflection will be
observed in the compass box, when a maximum current of 5 to 6 ampere flows in the circuit.
Now the position of the compensating coil is adjusted such that the aluminium pointer reads
0- O. It will be seen that, after this adjustment for any current in the circuit (below the
maximum current), the aluminium pointer will always read a - O. The current is brought to
minimum and then the circuit is switched off.
current is reduced in steps of 0.5 amps. When the current is 0.5 amps, the circuit switched off and the commutator reversed. Then
Observation
(i) To find tan θ
Adithya Institute of Technology Page 61
Physics Laboratory Manual
S.No.Current (I)
Ampere
Deflections in the Compass box Tan θ
degreesθ1 (deg) θ2 (deg) Mean
θ ( deg)
13
22.5
32
41.5
51
60.5
70
8-0.5
9-1.0
10-1.5
11-2.0
12-2.5
13
14-3.0
15
Adithya Institute of Technology Page 62
Physics Laboratory Manual-3.0
16-1.5
17-1.0
18-0.5
190
200.5
211.0
221.5
232.0
242.5
253.0
(i) To find the diameter of the rod
ZE = div
LC = 0.01 X 10-3m ZC = X 10-3m
Adithya Institute of Technology Page 63
Mean
Physics Laboratory Manual
S.NoPSR
X 10-3m
HSC
Div
HSR=HSC X
LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Mean diameter of the rod = ………………………… X 10-3m
Radius of the rod, r = …………………………. X 10-3m
Calculation.
be - 0.5 amp. Then the current is increased to its maximum value in steps of 0.5 amp up to –
5 amp. Again it is decreased to - 0.5 in steps of 0.5 amp. The circuit is switched off and
Adithya Institute of Technology Page 64
Physics Laboratory Manualcommutator reversed. Then the circuit is switched on and ammeter will read 0.5 amp. This is
considered to be + 0.5 amp. Again the current IS increased upto + 5 amp in steps of 0.5 amp.
This is called one cycle. Like this, by passing the current in cyclic order, the ferromagnetic
rod is magnetised and demagnetised alternatively.
When the operation is completed 20 times, the readings are recorded during the
21st and 22nd cycles. If these two sets of readings are not one and the same repeat 10 more
times before taking readings. All readings are recorded in table.
The distance between the compass box and rod d, the number of turns per metre
length of the solenoid, n, the radius of the rod r are determined. Using the readings, a graph
is drawn between the current (I in amp) in X axis and tan e in Y axis. This graph will be as
shown in fig.9.2. The area of the graph is also found out. Then the energy loss per unit
volume per cycle of magnetization is found out using the given formula.
Adithya Institute of Technology Page 65
Physics Laboratory Manual
Result
Hysteresis loss of the material of the given sample = …………………J/cycle/volume.
Adithya Institute of Technology Page 66
Physics Laboratory Manual
Expt. No:
Adithya Institute of Technology Page 67
Mgl3
4bd3s
Physics Laboratory ManualDate:
7. YOUNG’S MODULUS – NON UNIFORM BENDING
Aim:
To determine the young’s modulus of the material of a given rod by non- uniform
bending.
Apparatus Required:
A uniform rectangular beam made of wood or iron, two equal knife edges, a weight
hanger with slotted weights, vernier calipers. Screw gauge, Travelling microscope, pin, etc.,
Formula,
Young’s modulus of the material,
Y = Nm-2
Where
M- Load producing the depression ‘s’ (× 10-3 kg)
g – Acceleration due to gravity (9.8m/s2)
l - Length of the beam between two knife edges (× 10-2m)
b – Breadth of the beam(× 10-2m)
d – Thickness of the beam (× 10-3m)
s – Depression produced for a load ‘M’ (× 10-2m)
youngs modulus table
Adithya Institute of Technology Page 68
Physics Laboratory Manual
Procedure
Adithya Institute of Technology Page 69
Physics Laboratory ManualThe given beam is symmetrically placed over the knife edges. AB is the length of the
bam. At the center of the beam C a weight hanger is suspended. A pin is fixed vertically at C
using some wax. A Travelling microscope is focused on the tip of the pin. The beam is
brought to elastic mode by periodical loading and unloading. The reading in the vertical
scale of the microscope is noted. Weights are added in equal steps of M kg and the
corresponding readings are noted. The readings are noted while unloading also. The length
of the beam/(AB) between the knife edges is measured. The breadth (b) and thickness (d) of
the beam are measured with a vernier caliper and screw gauge respectively. The experiment
is repeated by changing the distance between the knife edges.
To find the breadth of the beam using vernier caliper(b)
Adithya Institute of Technology Page 70
Mean
Physics Laboratory Manual
E = div
LC = 0.01x10-2m ZC = x10-2m
S.N
O
MSR
×10-2m
VSC
Div
VSR=VSC X
L.C
×10-2m
Observed reading
OR= MSR + VSR
X 10-2m
Correct Reading
CR=OR ± ZC
X 10-2m
1
2
3
4
5
Adithya Institute of Technology Page 71
Physics Laboratory Manual
Calculations
M = ……………….. ×kg
g = 9.8ms-2
l = …………………×10-2m
b = …………………×10-2m
d = …………………×10-3m
s = …………………×10-2m
Adithya Institute of Technology Page 72
Physics Laboratory Manual
(iii) To find the thickness of the beam (d)
ZE = div
LC = 0.01 X 10-3m ZC = X 10-3m
S.NoPSR
X 10-3m
HSC
Div
HSR=HSC X
LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
Adithya Institute of Technology Page 73
Physics Laboratory Manual
Result
Young’s modulus of the given material of the rod = ………………….. … Nm-2.
Adithya Institute of Technology Page 74
Physics Laboratory Manual
Fig.1 Band gap of a Semiconductor
Model graph
Adithya Institute of Technology Page 75
Expt. No:
Date:
∆ lnR ∆
Physics Laboratory Manual
8. BAND GAP DETERMINATION OF A SEMICONDUCTORAim:
To determine the band gap energy of a semiconductor by studying the variation of the
resistance of the thermistor with varying temperature.
Apparatus require:
Thermistor, Ammeter, Voltmeter, Oven, Thermometer, Water bath etc.,
Formula,
Band gap Eg = 2 × kB × slope eV
Where Slope =
Rs – Resistance (ohm).
T – Absolute temperature (K)
kB – Boltzmann’s constant = 1.380662 × 10-23 J/K
Principle
A Semiconductor has the energy band structure of an insulator with the difference that
the forbidden energy gap is less than 2 eV. For germanium the energy band is 0.7 eV. And
for silicon it is 1.1 eV at 0 K. Energy of this magnitude cannot be imparted to an electron by
an applied electric field. Hence the valence band reminds full and conduction band empty.
These substances are insulators at room temperature. If the temperature is increased some of
the valence electrons may gain thermal energy greater than Eg. Consequently they move into
conduction band. When an electron moves from valence band to conduction band a
Observation: Determination of current for various temperatures
Power supply = ……………………… Volts
Adithya Institute of Technology Page 76
1T
V Is
Physics Laboratory Manual
Procedure
The circuit is as shown in figure (1). Themistor and the thermometer is immersed in a
water (or) oil bath, in such a way that the thermometer is kept near by the diode. The power
Adithya Institute of Technology Page 77
S.NoTemperatur
°C
Temperatur
K
1
T(K-1)
I
(× 10-6
amp)
Rs =
(Ohm)
ln Rs
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Physics Laboratory Manualsupply is kept constant (say 3 volts). The heating mantle is switched on and the oil bath is
heated up to 70°C. Now the heating mantle is switched off and the oil bath is allowed to cool
slowly. For every one degree, fall of temperature the micro ammeter reading (I) is noted.
A graph is plotted taking 1/T along x-axis and lnR along Y axis. A straight line is
obtained as shown in model graph. By finding the slope of the straight line, the band gap
energy can be calculated using the given formula. The same procedure can be repeated for
various constant power supply (4 volts, 5 volts).
Calculations
Slope =
kB = 1.380662× 10-23 J/K
Adithya Institute of Technology Page 78
Physics Laboratory Manual
Adithya Institute of Technology Page 79
Physics Laboratory Manual
Result
The band gap energy of the given thermistor, Eg = ……………………….. eV
Adithya Institute of Technology Page 80
Physics Laboratory Manual
Fig.1.Carey Foster's Bridge
Adithya Institute of Technology Page 81
R (l1-l2)
πr2X L
Physics Laboratory Manual
Expt. No:
Date:
9. CAREY FOSTER'S BRIDGE- SPECIFIC RESISTANCE OF A WIRE
Aim:
To determine the resistance of a given coil of wire and hence determine its specific
resistance using Carey Foster's bridge.
Apparatus Required:
A Carey Foster's bridge, Two equal (10 ohm) resistances, standard resistance box, 2V
DC regulated power supply, standard resistance box, Galvanometer, High Resistance , metal
and alloy wires and screw gauge.
Formula:
Resistance of the unknown coil X = R+ (l2- l1) x
Resistance per meter of the bridge wire,x = ohm/m
Specific resistance of a coil,
S = ohm.m
where
R – The resistance in the standard resistance box (Ohm)
x – Resistance per meter of the Carey foster bridge wire (ohm/m)
l1 – Balancing length when X is on the left gap and R is in the right gap (× 10-2m)
l2- Balancing length when X and R are interchanged (× 10-2m)
r – Radius of the resistance wire (× 10-2m)
L – Length of the resistance wire (× 10-2m)
Adithya Institute of Technology Page 82
Physics Laboratory ManualS – Specific resistance of the wire (ohm.m)
Observation
(i) Determination of resistance per meter (x) of the bridge:
Adithya Institute of Technology Page 83
S.No
Resistance
(R)
Ohms
Balancing length
x = R/( l1- l2)
ohm/m
l1
×10-2 m
l2
× 10-2 m
1
2
3
4
5
6.
Physics Laboratory ManualProcedure:
(i) Determination of the resistance per meter(x) of the bridge wire AB:
The connections are made as shown in the fig. P and Q is equal resistances, a
thick copper strip of 0 resistance is connected in the place of x and a standard low
resistance (0.1 ohm)in the place of R. The jockey is pressed near A and moved towards B
touching every point on the wire AB. The balancing point J1 is found out at which the
deflection in the galvanometer Zero. If J1 is the position of the jockey for null deflection, the
balancing length AJ1 (l1) is noted. The copper strip and the standard resistance interchanged.
Now the balancing length AJ2 is (l2) measured. The resistance per meter of the bridge wire
(r) is calculated by using the formula,
x= R/ (l2-l1) ohm/m
(ii) Determination of the unknown resistance (X) of the given wire:
Equal resistance P and Q are connected in the inner gaps. The resistance box R
is connected in the right gap and the given coil of unknown resistance X in the left gap. A 2
volt power supply is connected to the middle strip and the other terminal to the jockey
through a high resistance. A suitable resistance says 5 ohms is introduced in the resistance
box and the circuit is closed. The jockey is pressed near A and then near B. If the deflections
are in opposite directions the connections are correct. The jockey now pressed at the middle
of the bridge wire and the resistance in R is adjusted until the deflection in the galvanometer
(ii) Determination of unknown resistance (X) of the given coil
Adithya Institute of Technology Page 84
Physics Laboratory Manual
is almost zero. The value of resistance to be included in the resistance box R should be
rounded this value. If J1 is the balancing point, the balancing length AJ1 is measured. The
coil and R are interchanged. The new balancing length AJ2 is measured. The resistance of
the coil X is calculated by using the formula,
Adithya Institute of Technology Page 85
S.No Resistance
(R)
Ohm
Balancing length
X = R+( l2- l1)x
ohm
l1
×10-2 m
l2
× 10-2 m
1
2
3
4
5
6.
Physics Laboratory ManualX = R+(l1-l2)x ohm
(iii) Determination of the specific resistance of the given wire:
The resistance X of the wire is found as before. The length of the wire (L) is measured
after stretching it without any kink. The radius r of the wire is found with a screw gauge by
measuring its diameter at various points along the wire. The specific resistance of the wire is
calculated by using the formula (3).
(iii) Determination of diameter of the given coil
Least Count = 0.01 X 10-3m Zero Error = div
Zero Correction = X 10-3m
Adithya Institute of Technology Page 86
Physics Laboratory Manual
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Mean
Radius of the given coil (r) = ……………………… ×10-3m
Calculations,
Adithya Institute of Technology Page 87
Physics Laboratory Manual
Result
1. The resistance of the wire = ………………………… ohm.
2. Specific resistance of the
given wire. =………………………….. ohm-meter.
Adithya Institute of Technology Page 88
Physics Laboratory Manual
Fig.1. Viscosity of a liquid – Poiseuille’s flow
Adithya Institute of Technology Page 89
gr4 ht 8lV
Physics Laboratory ManualExpt. No:
Date:
10. CO-EFFICIENT OF VISCOSITY – POISEUILLE’S FLOW METHOD
Aim:
To determine the coefficient of viscosity of the given liquid by Poiseuille’s flow
method.
Apparatus Required:
Burette, Capillary tube, Travelling microscope, Beaker, Stop clock, Metre scale,
Rubber tube etc.,
Formula;
The coefficient of viscosity of the liquid = Nsm-2
Where ;
g – Acceleration due to gravity (9.8 ms-2)
- Density of water (1000 kg m-3)
r - Radius of the capillary tube (× 10-2 m)
l – Length of the capillary tube (× 10-2 m)
V – Volume of the flow of the liquid in cubic meter (10-6m3).
h - Mean pressure head (× 10-2 m)
t - Time taken for liquid flow
Adithya Institute of Technology Page 90
Physics Laboratory Manual
table,
Adithya Institute of Technology Page 91
Physics Laboratory ManualProcedure,
A clean graduated burette is vertically mounted. A capillary tube of length about 20
centimeters is connected to the bottom of the burette using a pinch cock provided at the
rubber tubing. The capillary tube is adjusted to be horizontal. The burette is filled with given
liquid. The pinch cock is completely opened and the liquid is allowed to flow. A beaker is
used to collect the out flowing liquid. When the liquid level crosses 0cc mark a stop clock is
started and the time is noted for the liquid level to reach 5,10,15….40cc.The readings are
tabulated then the vertical heights of the marks 0,5,10……40cc are measured from the
access of the capillary tube. From these measurements the mean pressure head (h) can be
calculated.
Adithya Institute of Technology Page 92
gr4 ht 8lV
Physics Laboratory Manual (ii) To determine diameter of the capillary tube
Least Count = 0.001x10-2m
Cross wire PositionMicroscope Readings Diameter
A ~ B
X 10-2m
MSR
X 10-2m
VSC
Div
TR= MSR+ (VSCx
LC) X 10-2mVertical crosswire
Left (A)
Right (B)
Horizontal
crosswire
Bottom (B)
Mean
Diameter of the capillary tube, d = ……………….×10-2 m
Radius of the capillary tube r = ………………. ×10-2 m
Length of the capillary tube, l = ………………. ×10-2 m
Calculations
Adithya Institute of Technology Page 93
Physics Laboratory Manual = Nsm-2
Density of the liquid, ρ = 1000kg/m3.
Acceleration due to gravity g = 9.8ms-2.
Radius of the capillary tube r = ……………….×10-2 m
Length of the capillary tube l = ……………….×10-2 m
Volume of the liquid V = ……………….×10-6 m3.
ht =……………….×10-2 m.sec
Calculation,
Adithya Institute of Technology Page 94
Physics Laboratory Manual
Adithya Institute of Technology Page 95
Physics Laboratory Manual
Result:
The coefficient of viscosity of the given liquid,
sm-2
Adithya Institute of Technology Page 96
Physics Laboratory Manual
Fig .1. Position of
spectrometer- Angle of the prism
Fig .2. Position of spectrometer- Angle of minimum deviation
Adithya Institute of Technology Page 97
(µv - µr ) ( µy -1)
Physics Laboratory ManualExpt. No:
Date:
11.SPECTROMETER – DISPERSIVE POWER OF THE PRISM
Aim
To determine the refractive index of the material of the prism for various colors in the
mercury light spectrum and hence to calculate its dispersive power.
Apparatus Required
Spectrometer, prism, mercury vapour lamp, prism holder and reading lens.
Formula
Refractive index, µ = (No unit)
Dispersive power of a prism, ω = (No unit)
Where,
A – Angle of the prism (degrees)
D – Angle of minimum deviation (degrees)
µv - Refractive index of the prism for violet line (No unit)
µr - Refractive index of the prism for red line (No unit)
µy - Refractive index of the prism for red line(No unit
Procedure:
(i) Determination of angle of prism (A)
The given prism is mounted vertically at the centre of the prism table with its refracting edge
facing the collimator. Now the parallel rays of light emerging out from the collimator falls
alm0st equally on the two faces of the prism ABC as shown in Fig.1. The telescope is turned
Adithya Institute of Technology Page 98
Sin
Sin
A+D 2
A2
Physics Laboratory ManualTABLE
Adithya Institute of Technology Page 99
Physics Laboratory Manualto catch the reflected image from one face of' the prism and fixed in that position. The tan-
gential screw is adjusted until the vertical cross-wire coincides with the fixed edge of the im-
age of the slit. The readings on both the verniers are noted. Similarly the readings corre-
sponding to the reflected image of the slit on the other face are also taken. The difference be-
tween the two readings of the same vernier gives twice the angle of the prism. Hence, the an-
gle of the prism 'A' is determined.
(ii) Determination of angle of minimum deviation (D)
The prism table is rotated so that the beam of light from the collimator is incident on
one face of the prism and emerges out from the other face. The telescope is rotated to catch
the refracted image of the yellow slit. The prism table is rotated in such a direction so that
the refracted image moves towards the direct beam. The telescope is rotated carefully to
have the image in the held of view. At one stage, the image stops momentarily and turns
back. This is the position of the minimum deviation. The telescope is rotated and made to
coincide with the violet slit. The telescope is fixed in this position and refracted ray reading
of the telescope is noted. The experiment is repeated for red slit. The prism is removed and
the direct reading of the slit is taken. The difference between the direct reading and the re-
fracted ray reading corresponding to the minimum deviation gives the angle of minimum de-
viation 'D'. The dispersive power is calculated using the given formula.
Adithya Institute of Technology Page 100
Physics Laboratory ManualTable
Adithya Institute of Technology Page 101
µ2 + µ1
2(µ1 ~ µ2) (µ - 1)
Physics Laboratory Manual
(iii) To find dispersive power of the prism
S.Noµ1
(No unit)
µ1
(No unit)
µ1 ~ µ2
(No unit)
µ =
(No unit)
ω =
(No unit)
Adithya Institute of Technology Page 102
Physics Laboratory Manual
Calculation,
Adithya Institute of Technology Page 103
Physics Laboratory Manual
Result
1. Angle of the prism A = …………………degrees.
2. Angle of the minimum deviation D = ………………...degrees
3. Refractive index of the material of the prism µ = ………………… (No unit)
4. Dispersive power of the given prism = …………………(No unit)
Adithya Institute of Technology Page 104
Physics Laboratory Manual
Adithya Institute of Technology Page 105
3MDgl2
2bd3s
Physics Laboratory ManualExpt. No:
Date:
12. YOUNG’S MODULUS – UNIFORM BENDINGAim :
To determine the young’s modulus of the material of a given rod by uniform bending.
Apparatus Required;
A uniform rectangular beam made of wood or iron, two equal knife edges, two weight
hangers with slotted weights, vernier caliper, Screw gauge, Travelling microscope, pin, etc.,
Formula:
Young’s modulus of the material,
Y = Nm
Where,
M- Load producing the depression‘s’ (× 10-3 kg)
D – Distance between the weight hanger and any one of the adjacent knife edge (× 10-2m)
g – Acceleration due to gravity (9.8m/s2)
l - Length of the beam between two knife edges (× 10-2m)
b – Breadth of the beam (× 10-2m)
d – Thickness of the beam (× 10-2m)
s – Elevation produced for a load ‘M’ (× 10-2m)
Adithya Institute of Technology Page 106
Physics Laboratory ManualTabulation,
S.NoLoad10-3
Kg
Microscope Reading 10-2 m Elevation for M x10-3Kg
Y x 10-2m
Loading Unloading Mean10 -2 m
MSR10-2 m
VSCdiv
TR10 -2 m
MSR10-2m
VSC
div
TR
10-2m
1.
2.
3.
4.
5.
6.
Adithya Institute of Technology Page 107
Physics Laboratory ManualProcedure
The given beam is symmetrically placed over the knife edges. AB is the length of the
beam. Two weight hangers are suspended, one each on either side of the knife edge at equal
distance from the knife edge. A pin is fixed vertically exactly at the center of the beam i.e. at
C using some wax. A Travelling microscope is focused on the tip of the pin. The beam is
brought to elastic mode by periodical loading and unloading of weights on both the weight
hangers simultaneously. The reading in the vertical scale of the microscope is noted.
Weights are added in equal steps of M kg on both the weight hangers and the corresponding
readings are noted. The readings are noted while unloading also. The length of the beam the
weight hanger and any one of the adjacent knife edge (D) is measured. The breadth (b) and
thickness (d) of the beam are measured with a vernier caliper and screw gauge respectively.
The experiment is repeated by changing the distance between the knife edge and the weight
hangers.
Adithya Institute of Technology Page 108
Mean
Physics Laboratory Manual(ii) To find the breadth of the beam using vernier caliper (b)
ZE = divLC = 0.01cm ZC = cm
S.N
O
MSR
× 10-2m
VSC
Div
VSR=VSC X
L.C
× 10-2m
Observed reading
OR= MSR + VSR
× 10-2m
Correct Reading
CR=OR ± ZC)
× 10-2m
1
2
3
4
5
Breadth of the beam (b) = ………….×10-2m
Adithya Institute of Technology Page 109
Physics Laboratory ManualCalculations
M = ……………….. kg
g = 9.8ms-2
D = ………………..×10-2m
l = …………………×10-2m
b = …………………×10-2m
d = …………………×10-2m
s = …………………×10-2m
Adithya Institute of Technology Page 110
Physics Laboratory Manual
(iii) To find the thickness of the beam (d)
ZE = div
LC = 0.01 X 10-3m ZC = X 10-3m
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Thickness of the beam (d) = …………………. ×10-3m
Adithya Institute of Technology Page 111
Mean
Physics Laboratory Manual
Result
Young’s modulus of the given material of the rod = ………………….. … Nm-2.
Adithya Institute of Technology Page 112
Physics Laboratory Manual
Fig .1 Torsional pendulum
Expt. No:
Date:
Adithya Institute of Technology Page 113
2m (d22 – d 1
2 ) To 2 ( T2
2-T12)
8πI l r4 To
2
Physics Laboratory Manual
13. TORSIONAL PENDULUM- RIGIDITY MODULUS
Aim:
To determine
(i) the moment of inertia of a disc and
(ii) rigidity modulus of the material of a wire by Torsional oscillations.
Apparatus required;
Torsion pendulum, two equal cylindrical masses, Stop clock , Screw gauge, Meter
scale etc.,
Formula:
Moment of inertia of the disc I = Kgm2
Rigidity modulus of the material of the wire n = Nm-2. Wherem- Mass of each of the two symmetrical weights placed on the disc (×10-3kg)
d1 – Closest distance between suspension wire and the centre of mass of a cylinder (×10-2m)
d2 - Farthest distance between suspension wire and the centre of mass of a cylinder ×10-2m
To – Time period of oscillation without any weights (sec.)
T1 – Time period when two equal masses placed on the disc at a distance d1(sec.)
T2 – Time period when two equal masses placed on the disc at a distance d2(sec.)
l- Length of the suspension wire(×10-2m)
r- Radius of the wire(×10-3m)
Adithya Institute of Technology Page 114
Physics Laboratory Manual(iii) To find period of oscillation (T):
Procedure
One end of a long, uniform wire whose rigidity modulus is to be determined is
clamped by a vertical chuck. To the lower end, a heavy uniform circular disc is attached by
another chuck. The length of the suspension 'l' is fixed to a particular value (say 60 cm or 70
cm). The suspended disc is slightly twisted so that it executes torsional oscillations. Care is
taken to see that the disc oscillates without wobbling. The first few oscillations are omitted.
By using the pointer, (a mark made in the disc) the time taken for 10 complete oscillations
are noted.Two trials are taken. The meantime period T0 (time for one oscillation) is found.
Two equal cylindrical masses are placed on the disc symmetrically on either side, close to
the suspension wire (at the minimum distance). The closest distance 'd l' from the centre of
the mass of the cylinder and the centre of the suspension wire is found. The disc with masses
at distance 'dl' is made to executive torsional oscillations by twisting the disc. The time taken
for 10 oscillations is noted. Two trials are taken. Then the mean time period 'T l' is
Adithya Institute of Technology Page 115
Position of masses
Time period for 10 oscillationsTime period for one oscillation
seconds
Trial – 1seconds
Trial - 2seconds
Meanseconds
Without any masses
To =
With masses at closest distance d1 = cm T1 =
With masses at closest distance d1 = cm T2 =
Physics Laboratory Manualdetermined.
Two equal masses are now moved to the extreme ends so that the edges of masses
coincide with the edge of the disc and the centres are equi-distant. The distance 'd 2' from the
centre of the mass of the cylinder and the centre of the suspension wire is noted. The disc
with masses at distance 'd2' is allowed to execute tensional oscillations by twisting the disc.
The time taken for 10 oscillations is noted and time period 'T2' is calculated. The diameter of
the wire is accurately measured at various places along its length with screw gauge. From
this, the radius of the wire is calculated. The moment of inertia of the disc and the rigidity
modulus of the wire are calculated using the given formulae.
Calculations
Mean radius of the wire r = ……………………….×10-3m
Length of the wire l = …………………………×10-2m
Mass of one of the symmetrical weights m = ………………………..×10-2m
Distance at which masses are placed closest d1 = ………………………..×10-2m
Distance at which masses are placed farthest d2 = ……………………….×10-2m
Period of oscillations without any weights T0 = ……………………… secs
Period of oscillations with masses at d1 T1 = ……………………….secs
Period of oscillations with masses at d2 T2 = ……………………….secs
Adithya Institute of Technology Page 116
Physics Laboratory Manual
(ii) Determination of the diameter of a wire:
ZE = div LC = 0.01mm ZC = mm
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
1
2
3
4
5
Adithya Institute of Technology Page 117
Physics Laboratory Manual
S.N
O
PSR
X 10-3m
HSC
Div
HSR=HSC X LC
X 10-3m
Observed reading
OR= PSR + HSR
X 10-3m
Correct Reading
CR=OR ± ZC
X 10-3m
Diameter of the suspension wire = …………………. ×10-3m
Adithya Institute of Technology Page 118
Mean
Physics Laboratory Manual
Result
Moment of inertia of the disc (I) =…………………………….. kgm2
Rigidity modulus .of the material of the wire n = ……………………………. Nm - 2
Adithya Institute of Technology Page 119