Chapter 14. Characteristics of Light Section 14.1.
-
Upload
ralf-simon -
Category
Documents
-
view
224 -
download
1
Transcript of Chapter 14. Characteristics of Light Section 14.1.
![Page 1: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/1.jpg)
Chapter 14
![Page 2: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/2.jpg)
Characteristics of LightCharacteristics of Light
Section 14.1
![Page 3: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/3.jpg)
Electromagnetic WavesElectromagnetic Waves
Light is made of electromagnetic waves.Take a prism and break up white light into a rainbow
like band of colors. These are all in the visible spectrum.
Red, orange, yellow, green, blue, indigo and violet.ROY G BIV
![Page 4: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/4.jpg)
![Page 5: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/5.jpg)
Electromagnetic WavesElectromagnetic Waves
The spectrum also includes non-visible electromagnetic waves, such as x-rays, microwaves, radio waves, and radiation.
Because they all are electromagnetic waves they all have similar properties.
![Page 6: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/6.jpg)
Electromagnetic WavesElectromagnetic Waves
Electromagnetic waves are transverse waves consisting of oscillating electric and magnetic fields at right angles to each other.
Oscillate: to have a periodic vibration
![Page 7: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/7.jpg)
![Page 8: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/8.jpg)
Electromagnetic WavesElectromagnetic Waves
Electromagnetic waves vary depending on frequency and wavelength
All electromagnetic waves move at the speed of light
![Page 9: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/9.jpg)
Electromagnetic WavesElectromagnetic Waves
We will use 3.00 X 108 m/s as the speed of light, c.
The wave speed equation is:
c = f Speed of light = frequency X wavelength
![Page 10: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/10.jpg)
Sample ProblemSample Problem
The AM radio band extends from 5.4 X 105 Hz to 1.7 X 106 Hz. What are the longest and shortest wavelengths in this frequency range?
f 1 = 5.4 x 105 Hz f 2 = 1.7 x 106 Hzc = 3.0 x 108 m/sc = f= c/ f
1 = 5.6 x 102 m
2 = 1.8 x 102m
![Page 11: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/11.jpg)
Light travels in straight lines.Light travels in straight lines.
Light travels in straight lines.• Show the laser on the wall. Put an index card in
the beam. This shows that the light is traveling in a straight line, but you can only see it when it hits something.
• Put some chalk dust in the beam to show it is continuous.
Brightness decreases by the square of the distance form the source
• Show how the size of the dot the laser makes gets bigger as it gets further from the source.
Laser
![Page 12: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/12.jpg)
The brightness of light is inversely proportional to the square of the distance from the light source.Ex. If you move twice as far away from the light source, ¼ as much light falls on the book.
![Page 13: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/13.jpg)
Flat mirrorsFlat mirrors
Section 14.2
![Page 14: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/14.jpg)
Reflection of LightReflection of Light
Reflection – the turning back of an electromagnetic wave at the surface of a substance
![Page 15: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/15.jpg)
Clear vs. Diffuse ReflectionClear vs. Diffuse Reflection
Specular reflection: light reflected from smooth shiny surfaces
In specular reflection the incoming and reflected angles are equal (=’)
Diffuse reflection: light is reflected from a rough textured surface
![Page 16: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/16.jpg)
Diffuse Reflection: Diffuse Reflection: Definition, Examples and Definition, Examples and
SurfacesSurfaces
http://education-portal.com/academy/lesson/diffuse-reflection-definition-examples-surfaces.html#lesson
![Page 17: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/17.jpg)
Part 2 - ReflectionPart 2 - ReflectionReflection from a mirror:
Incident ray
Normal
Reflected ray
Angle of incidence
Angle of reflection
Mirror
![Page 18: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/18.jpg)
Reflection of LightReflection of Light
Angle of incidence – the angle between a ray that strikes a surface and the normal to that surface at the point of contact.
Angle of reflection – the angle formed by the line normal to a surface and the direction in which a reflected ray moves
Normal is a line perpendicular to the reflection surface.
![Page 19: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/19.jpg)
The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection
In other words, light gets reflected from a surface at THE SAME ANGLE it hits it.
The same !
!!
![Page 20: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/20.jpg)
Reflection: Angle of Reflection: Angle of Incidence and Curved Incidence and Curved
SurfacesSurfaces
http://education-portal.com/academy/lesson/reflection-definition-angles-of-incidence-diffuse-reflection.html#lesson
![Page 21: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/21.jpg)
Drawing a Reflected Drawing a Reflected ImageImage
Use ray diagrams to show image location
We will find the virtual image (the image formed by light rays that only appear to intersect)
![Page 22: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/22.jpg)
![Page 23: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/23.jpg)
Drawing a Reflected Drawing a Reflected ImageImage
Draw the object in front of the mirrorDraw a ray perpendicular to the mirror’s surface. Because this
is 0 from normal, the angle is the same from the mirror to the virtual object
Draw a second ray that is not perpendicular to the mirror’s surface from the same point to the surface of the mirror.
Next, trace both reflected rays back to the point from which they appear to have originated, that is, behind the mirror. Use dotted lines when drawing lines that that appear to emerge from behind the mirror. The point at which the dotted lines meet is the image point.
![Page 24: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/24.jpg)
Flat MirrorsFlat Mirrors
Image is VIRTUAL, UPRIGHT, UNMAGNIFIED
![Page 25: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/25.jpg)
Chapter 14Chapter 14
14.3 Concave Mirrors
![Page 26: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/26.jpg)
Spherical MirrorsSpherical MirrorsA spherical mirror has the shape of part of
a sphere’s surface. The images formed are different than those of flat mirrors.
Concave mirrors were silvered on the inside of the sphere and convex mirrors were silvered on the outside of the sphere.
![Page 27: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/27.jpg)
Concave Spherical Mirror Concave Spherical Mirror
An inwardly curved, mirrored surface that is a portion of a sphere and that converges incoming light rays.
![Page 28: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/28.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
![Page 29: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/29.jpg)
• Principle axis - the line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror
• Center of curvature - the point in the center of the sphere from which the mirror was sliced (C)
• Vertex - the point on the mirror's surface where the principal axis meets the mirror (A)
![Page 30: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/30.jpg)
• Focal point - midway between the vertex and the center of curvature (F)
• Radius of curvature - the distance from the vertex to the center of curvature (R)
• Focal length - the distance from the mirror to the focal point, one-half the radius of curvature (f)
• http://www.youtube.com/watch?v=np8lENrge0Q
• http://www.youtube.com/watch?v=jrje73EyKag
![Page 31: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/31.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
The light bulb is distance p away from the center of the curvature, C. Light rays leave the light bulb, reflect from the mirror and converge at distance q in front of the mirror. Because the reflected light rays pass through the image point, the image forms in front of the mirror.
![Page 32: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/32.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
If you were to place a sheet of paper at the image point, you would see a clear, focused image of the light bulb (a real image). If the paper was placed in front of or behind the image point, the image would be unfocused.
![Page 33: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/33.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
Real image – an image formed when rays of light actually intersect at a single point
Focal length – equal to half the radius of curvature of the mirror.
![Page 34: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/34.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
Mirror equation: 1/p + 1/q = 2/R
1 + 1 = 2 .
Object distance Image distance radius of curvature
Or: 1/p + 1/q = 1/f
1 + 1 = 1 .
Object distance Image distance focal length
![Page 35: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/35.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
Object and image distances have a positive sign when measured from the center of the mirror to any point on the mirror’s front side.
Distances for images that form on the backside of the mirror always have a negative sign.
![Page 36: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/36.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
The measure of how large or small the image is with respect to the original object is called the magnification of the image.
M = h’/h = -(q/p)
Magnification = image height = image distance
object height object distance
![Page 37: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/37.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
For spherical mirrors, three reference rays are used to find the image point. The intersection of any two rays locates the image. The third ray should intersect at the same point and can be used to check the diagram.
![Page 38: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/38.jpg)
Rules for drawing reference Rules for drawing reference raysrays
Ray Line drawn from object to mirror
Line draw from mirror to image after reflection
1 Parallel to principal axis Through focal point F
2 Through focal point F Parallel to principal axis
3 Through center of curvature C
Back along itself through C
![Page 39: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/39.jpg)
Ray 1Ray 1
![Page 40: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/40.jpg)
Ray 2Ray 2
![Page 41: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/41.jpg)
Ray 3Ray 3
![Page 42: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/42.jpg)
All three rays togetherAll three rays together
![Page 43: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/43.jpg)
Spherical Mirrors - Spherical Mirrors - ConcaveConcave
Image is REAL, INVERTED, and DEMAGNIFIED !!!
C F
![Page 44: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/44.jpg)
Concave Spherical MirrorConcave Spherical Mirror
When an object changes its location in relation to the mirror, its image changes in location, and form.
![Page 45: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/45.jpg)
Concave Spherical MirrorConcave Spherical Mirror
Object’s distance
Type of Image Location of Image
Greater than focal length
Real and inverted
In front of mirror
At the focal length
Image is infinitely away from mirror and can’t be seen
Between focal point and mirror’s surface
Virtual and upright
Behind mirror
![Page 46: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/46.jpg)
Distance greater than focal Distance greater than focal lengthlength
![Page 47: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/47.jpg)
Distance = focal lengthDistance = focal length
![Page 48: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/48.jpg)
Between focal length and Between focal length and mirrormirror
![Page 49: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/49.jpg)
Spherical Mirrors – ConcaveSpherical Mirrors – ConcaveObject Inside the Focal Object Inside the Focal
PointPoint
Image is VIRTUAL, UPRIGHT, and MAGNIFIED
C F
![Page 50: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/50.jpg)
Concave Spherical Concave Spherical MirrorsMirrors
![Page 51: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/51.jpg)
![Page 52: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/52.jpg)
M= -(q/p)We have p, but not q, so we need another
equation to find q.1/p + 1/q = 1/fWe have p and f, so we can solve for q.1/q = 1/f – 1/p
![Page 53: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/53.jpg)
1/q = 1/f – 1/pSubstitute:(1/10 cm) – (1/30 cm) = 1/qSolve:0.06667 cm = 1/qq= 15 cm
![Page 54: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/54.jpg)
Now with q we can substitute into the original formula and solve.
M= -(q/p)M= -(15 cm/30cm)
M= -0.50This means that the image is smaller than
the object and inverted. Therefore it is a real image.
![Page 55: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/55.jpg)
Spherical Mirrors - Spherical Mirrors - ConvexConvex
Convex spherical mirror:An outwardly curved, mirrored surface that is a portion of a sphere and that diverges incoming light rays
The focal point and center of curvature are situated behind the mirror.
![Page 56: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/56.jpg)
Spherical Mirrors - Spherical Mirrors - ConvexConvex
Convex mirrors take the objects in a large field of view and produce a small image, but give a the observer a complete view of a large area.
Examples:In stores, the passenger’s side of a car
![Page 57: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/57.jpg)
Spherical Mirrors - Spherical Mirrors - ConvexConvex
Image is VIRTUAL, UPRIGHT, and DEMAGNIFIED
C F
![Page 58: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/58.jpg)
ColorColor
White light is not a single color; it is made up of a mixture of the seven colours of the rainbow.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.
![Page 59: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/59.jpg)
Wavelengths of LightWavelengths of Light
Red Light – nm
Green Light - nm
Blue Light - nm
![Page 60: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/60.jpg)
Adding colorsAdding colorsWhite light can be split up to make separate
colors. These colors can be added together again.
The primary colors of light are red, blue and green:Adding blue and
red makes magenta (purple)
Adding blue and green makes cyan
(light blue)
Adding all three makes white again
Adding red and green makes yellow
![Page 61: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/61.jpg)
Seeing colorSeeing colorThe color an object appears depends on the
colors of light it reflects.
For example, a red book only reflects red light:
White
light
Only red light is
reflected
![Page 62: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/62.jpg)
A white hat would reflect all seven colors:
A pair of purple pants, in addition to being ugly, would reflect purple light
(or red and blue, as purple is made up of red and blue):
Purple light
White
light
![Page 63: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/63.jpg)
Using colored lightUsing colored light
If we look at a colored object in colored light we see something different. For example, consider the outfit below – I mean, from a physics standpoint, not as a fashion choice:
White
light
Shorts look blue
Shirt looks red
![Page 64: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/64.jpg)
In different colours of light this kit would look different:
Red
lightShirt looks red
Shorts look black
Blue
light
Shirt looks black
Shorts look blue
![Page 65: Chapter 14. Characteristics of Light Section 14.1.](https://reader036.fdocuments.us/reader036/viewer/2022062301/56649ef05503460f94c01704/html5/thumbnails/65.jpg)
Using filtersUsing filtersFilters can be used to “block” out different colors of
light:
Red Filte
r
Magenta
Filter