PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

1. Figure 2 shows monochromatic light X incident towards A on a vertical screen.

When the semicircular glass block is placed across the path of light with

its flat face parallel to the screen, a bright spot is formed at A. When the glass block is rotated about a horizontal axis through O, the bright spot moves down from A towards B and then just disappears at B, a distance 1.68cm from A.(i) Find the refractive index of the material of the glass block.(ii) Explain whether AB would be longer or shorter if a block of

glass of a higher refractive index was used 2. Two long straight conductors P and Q which are 5.0cm apart in air carry

currents of 16A and 8A respectively as shown in figure.

(i) Sketch the magnetic field pattern due to the current through two

conductors .(ii) Calculate the force on the conductor P if it is 50cm long.

P8A16A

5.0cm .

Fig.3

Q

B

AX O

Screen.

Figure 2

1.68cm

1.5cm

Semi-circular glass block.

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

3. A bar magnet is suspended by a spring so that can oscillate freely in and out of the coil as shown in figure 7.

The coil is connected to a cathode ray oscilloscope (CRO),which has its time base is on. The oscilloscope is adjusted to obtain a trace on its screen.

(a) Explain why an emf is induced in the coil when the magnet is oscillating inside the coil.

(b) Sketch a graph showing the variation of the emf induced in the coil with time as observed on the screen of the oscilloscope.

4. A tuning capacitor of two semi-circular plates which are separated by an air gap of 1mm is as shown in figure 1.

When the tuning capacitor shown above is used with a 10mH inductor to in an LC circuit of a radio to provide tuning all radio stations in the band from 500kHz to 1.50MHz. Find the

(i) largest value of capacitance of the tuning capacitor.

Coil

N

S

CRO

Oscillating magnet

Fig. 7

Movable plate Fixed plate

Tuning knob

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

(ii) diameter of the plates of the tuning capacitor.

5. A copper ring is suspended by a long light rod pivoted at X so that it can swing as a pendulum as shown in figure 4. An electromagnet is mounted so that the ring passes over it as it swings.

When switch k is open ring is given a slight displacement and then released to oscillate between points A and B. Explain what

(i) happens to the motion of the ring when the switch k is closed.(ii) would happen to the motion of the ring if it has a slit.

6. A small magnet is attached to a spring as shown in figure 3.

Switch k is closed and the magnet is displaced downwards slightly and released to oscillate vertically. Explain:(i) the observation made

S

N

Fig.3

BA

k

Electromagnet

X

Copper ring

Suspending rod

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

(ii) why the magnet takes long to come to rest when switch k is opened.

7. A plane mirror M is placed in front of a glass prism of refractive index 1.50 such that its reflecting surface is parallel to the face AB of the prism. The refracting angle of the prism is 38o . A ray of monochromatic light is incident normally to the face AB of the prism and after refraction at the face BC of the prism it is reflected from the plane mirror as shown in figure 8.

Determine the refractive index of the material of the glass. (4 mark

8. An object is placed at the bottom of a tank containing two different liquids which do not mix with each other. The depths of the lower and upper liquids are ℎ and ℎ respectively. If the refractive indices of the lower and upper liquids are and respectively, show that the apparent depth of the object when viewed directly from above the tank

is given by ( ℎ11 + ℎ2

2 ).

9. A fully charged capacitor of capacitance C is discharged through a small coil of resistance wire embedded in a thermally insulated metal block of specific heat capacity S and mass m. If the

M

59o

38o

B

CA

Fig.8

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

temperature of the block is raised by T , show that the potential

difference V across the capacitor is C

TmS2 .

10. A parallel plate capacitor with square plates of length L has capacitance C when there is air between the plates. The capacitor is charged to a p.d

V Oand then isolated. A dielectric slab of relative permittivity and length

L is slowly inserted so that it just fills the space between the plates of the capacitor. At a certain instant, the dielectric slab is at a distance x into the gap as shown in the figure 5.

Show that the potential difference between the plates of the capacitor is given

by = ( ) .

(a) (i) Find an expression for the energy stored in the capacitor when the dielectric slab is in the position shown in the figure 5. Give your answer in terms of , , , and .

(ii) Sketch a graph to show the variation of energy stored in the capacitor with distance the slab is inserted (3 marks)

x

L

L

d

Fig.5

dielectric

Capacitor plates

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

11. A ray of light traveling in a liquid is incident at angle of 58o at the liquid –glass interface. At A the ray of light suffers total internal reflection and at B it grazes the glass-air interface as shown in figure 6.

If the refractive index of the material of glass is 1.5 , find the

(i) critical angle for glass(ii) refractive index of the liquid.

deviation , ,that the ray suffers at the liquid glass interface

12. (a) Give 4 differences between virtual and real images.(b) The diagram in figure 2 shows a convex mirror M1 and a plane mirror

M2. O is a real extended object placed in front of the mirrors.

If the image of O by no parallax between the images of M1 and M2 is I, find the radius of curvature of the convex mirror.

(c) Figure 4 shows a real point object O, placed on the principal axis,15cm from in front of a concave mirror M of radius of curvature 20.0cm.

A cubic glass block of side 9.0cm and refractive index 1.5 is placed between O and M , with one of its edges parallel to the principal axis.

M1

M2

IO

20cm

15cm

Fig.2

B

A

58o

Fig.6

Glass

Liquid

Air

PHYSICS REVSION QUESTIONS

compiled by Balayo isaac

Determine the displacement of the image as a result of introducing the glass block between the object O and the mirror M.

MO

15cm Fig.4

n=1.5

Glass block

9.0cm