Reflection Of Light Flashcards
1
Q
What is light?
A
A form of energy called luminous energy.
2
Q
What do luminous sources of light do?
A
Generate and emit light by themselves.
3
Q
Give examples of luminous sources of light.
A
The sun
4
Q
What are non-luminous bodies?
A
Those that depend on natural or artificial light sources to illuminate them.
5
Q
How are non-luminous bodies seen?
A
Only when they reflect the light from a luminous body.
6
Q
Give examples of non-luminous bodies.
A
A page of a book
7
Q
What is a light ray?
A
The direction or path along which light energy flows.
8
Q
What is a beam of light?
A
A collection of rays.
9
Q
What is a parallel beam of light?
A
One in which the light rays are parallel to one another.
10
Q
What is a convergent beam of light?
A
One in which the rays converge or meet at a point.
11
Q
What is a divergent beam of light?
A
One in which the light rays all come from a point and spread out or diverge from the source.
12
Q
State the rectilinear propagation of light.
A
Light travels in straight lines.
13
Q
What is a shadow?
A
An area in which light rays from a source cannot reach.
14
Q
How is a shadow produced?
A
By the obstruction of light by an opaque object.
15
Q
What is an eclipse?
A
A result of a shadow cast by one heavenly body on another.
16
Q
What is a solar eclipse?
A
When the Moon is between the Sun and the Earth
17
Q
What is an annular eclipse?
A
When the Earth and the Moon are in positions where the extreme rays at the Moon’s edge intersect before reaching the Earth
18
Q
What is a lunar eclipse?
A
When the Earth is between the Sun and the Moon
19
Q
What is a pinhole camera?
A
A light-proof box with a small hole at one end and a screen at the opposite end
20
Q
Is the image formed by a pinhole camera inverted or upright?
A
Inverted.
21
Q
What is magnification?
A
The ratio of the size (or height) of the image to the size (or height) of the object.
22
Q
What happens when light falls on a surface?
A
It is either absorbed
23
Q
What is regular reflection?
A
When parallel rays of light incident on a smooth or polished surface are reflected as parallel rays in one direction.
24
Q
What is diffuse reflection?
A
When parallel rays of light incident on a rough or irregular surface are reflected in various directions.
25
What is light?
A form of energy called luminous energy.
26
What do luminous sources of light do?
Generate and emit light by themselves.
27
Give examples of luminous sources of light.
The sun
28
What are non-luminous bodies?
Those that depend on natural or artificial light sources to illuminate them.
29
How are non-luminous bodies seen?
Only when they reflect the light from a luminous body.
30
Give examples of non-luminous bodies.
A page of a book
31
What is a light ray?
The direction or path along which light energy flows.
32
What is a beam of light?
A collection of rays.
33
What is a parallel beam of light?
One in which the light rays are parallel to one another.
34
What is a convergent beam of light?
One in which the rays converge or meet at a point.
35
What is a divergent beam of light?
One in which the light rays all come from a point and spread out or diverge from the source.
36
State the rectilinear propagation of light.
Light travels in straight lines.
37
What is a shadow?
An area in which light rays from a source cannot reach.
38
How is a shadow produced?
By the obstruction of light by an opaque object.
39
What is an eclipse?
A result of a shadow cast by one heavenly body on another.
40
What is a solar eclipse?
When the Moon is between the Sun and the Earth
41
What is an annular eclipse?
When the Earth and the Moon are in positions where the extreme rays at the Moon's edge intersect before reaching the Earth
42
What is a lunar eclipse?
When the Earth is between the Sun and the Moon
43
What is a pinhole camera?
A light-proof box with a small hole at one end and a screen at the opposite end
44
Is the image formed by a pinhole camera inverted or upright?
Inverted.
45
What is magnification?
The ratio of the size (or height) of the image to the size (or height) of the object.
46
What happens when light falls on a surface?
It is either absorbed
47
What is regular reflection?
When parallel rays of light incident on a smooth or polished surface are reflected as parallel rays in one direction.
48
What is diffuse reflection?
When parallel rays of light incident on a rough or irregular surface are reflected in various directions.
49
What is the law of reflection?
The angle of incidence is equal to the angle of reflection.
50
What is a plane mirror produced by?
Coating one side of a plane glass plate with silver.
51
Why is one side of a plane glass plate coated with silver?
The silvered surface prevents light rays that strike the glass from passing through the glass and serves to reflect the light.
52
What is the normal to the mirror?
The line that is perpendicular to the mirror.
53
What is the angle of incidence?
The angle between the incident ray and the normal.
54
What is the angle of reflection?
The angle between the reflected ray and the normal.
55
What is the law of reflection?
The angle of incidence is equal to the angle of reflection.
56
What is the principle of reversibility of light?
The path of a light ray is reversible.
57
What is a virtual image?
An image that cannot be caught on a screen.
58
What is a real image?
An image that can be caught on a screen.
59
What are the characteristics of an image formed by a plane mirror?
It is the same size as the object; It is virtual; It is laterally inverted; It is as far behind the mirror as the object is in front of the mirror; It is upright.
60
What is lateral inversion?
The effect of a plane mirror on objects placed in front of it whereby the appearance of the image looks like a reversal of the object.
61
How do you calculate the number of images formed by two mirrors placed at an angle to each other?
n = 360/θ - 1 (where n is the number of images
62
What is a Kaleidoscope?
A toy which uses the principle of multiple reflections to produce multiple images.
63
What is a Periscope?
An instrument used for looking over barriers or obstacles.
64
If the direction of an incident ray on a mirror is kept constant and the mirror is rotated through an angle
what happens to the reflected ray?
65
What is the formula relating the number of images (n) formed by two mirrors and the angle (θ) between them?
n = 360/θ - 1
66
What is a practical application of reflection by plane mirrors?
The Periscope.
67
What is a Periscope used for?
Looking over barriers or obstacles.
68
Describe a simple periscope.
It consists of two parallel plane mirrors fixed facing one another and inclined at 45° to the walls of the tube in which the mirrors are fixed.
69
If the direction of an incident ray on a mirror is kept constant and the mirror is rotated through an angle
what happens to the reflected ray?
70
Explain how a simple periscope works.
A horizontal ray of light from the object falls on the first mirror at an angle of 45° to the normal. As the angle of incidence is equal to the angle of reflection
71
What is a disadvantage of the periscope?
It often produces multiple images.
72
If the direction of an incident ray on a mirror is kept constant and the mirror is rotated through an angle
what happens to the reflected ray?
73
In the context of reflection
what is a normal?
74
Explain the relationship between the angle of incidence (i) and the angle of reflection (r).
The angle of incidence (i) is equal to the angle of reflection (r).
75
If a light ray is incident on a plane mirror at an angle
how is it reflected?
76
What is the angle of deviation (d) of a light ray reflected by a mirror?
d = 180 - (i + r) or d = 180 - 2i (since i = r).
77
State the laws of reflection.
1. The incident ray
78
What is the principle of reversibility of light?
The path of a light ray is reversible.
79
Describe the image formed by a plane mirror.
Virtual
80
Can a virtual image be caught on a screen?
No.
81
Can a real image be caught on a screen?
Yes.
82
What causes lateral inversion in a plane mirror?
The fact that an object is perpendicularly opposite its image behind the mirror.
83
What is the formula to calculate the number of images formed by inclined mirrors?
n = (360/θ) - 1
84
If two mirrors are placed at 90 degrees to each other
how many images will be formed?
85
If two mirrors are placed parallel to each other
how many images will be formed?
86
What is a Kaleidoscope?
A toy that uses inclined mirrors to produce multiple images.
87
At what angle are the mirrors inclined in a Kaleidoscope?
60 degrees
88
What is a Periscope?
An instrument used for looking over barriers or obstacles.
89
How does a Periscope work?
It uses two parallel plane mirrors inclined at 45 degrees to the walls of the tube to reflect light from an object to the observer's eye.
90
What is a disadvantage of a Periscope?
It often produces multiple images.
91
If a mirror is rotated through an angle while the incident ray remains constant
through what angle does the reflected ray rotate?
92
Explain why the reflected ray rotates twice the angle of the mirror's rotation.
This can be proven using the laws of reflection and geometry. When the mirror rotates
93
What is this principle of mirror rotation used for?
It is used in mirror galvanometers for measuring very small electric currents and in the navigator's sextant.
94
What is the use of totally reflecting prisms in periscopes?
To produce only one image
95
What are the angles of the prisms used in periscopes?
90 degrees
96
What is the advantage of using prisms over plane mirrors in periscopes?
Prisms produce only one image.
97
At what angle of incidence does total internal reflection occur in a glass prism?
Angles greater than the critical angle for glass (approximately 42 degrees).
98
What is the angle between the incident ray and the emergent ray in a prism?
Angle of deviation.
99
When does minimum deviation occur in a prism?
When the angle of incidence equals the angle of emergence (i = e).
100
What is the shape of a prism that produces minimum deviation?
Equilateral triangular prism
101
What is the relationship between the angle of incidence and the angle of emergence at minimum deviation?
They are equal
102
What is the refracted ray's orientation when a ray passes symmetrically through the prism?
Parallel to the base of the prism
103
When light travels from air to glass
does it bend towards or away from the normal?
104
When light travels from glass to air
does it bend towards or away from the normal?
105
What is the angle of deviation in a prism?
The angle between the incident ray and the emergent ray.
106
Does a prism displace the light?
Yes
107
Does a rectangular glass block displace the light?
Yes
108
What is the formula for the refractive index of the material of the prism (n) in terms of the refracting angle (A) and the angle of minimum deviation (D)?
n = sin((A+D)/2) / sin(A/2)
109
What is the condition for minimum deviation in a prism?
The incident and emergent rays are equally inclined to their respective surfaces (i = e).
110
What is a totally reflecting prism?
A right-angled isosceles prism that can be used to deviate a ray of light through 90 degrees or 180 degrees using total internal reflection.
111
What is an application of total internal reflection?
Mirages
112
What is the approximate value of the critical angle for light traveling from glass to air?
42 degrees
113
What is the real depth?
The actual depth of an object below the surface of a medium.
114
What is the apparent depth?
The depth at which an object appears to be when viewed from another medium due to refraction.
115
What is the relationship between real and apparent depth and refractive index?
Refractive index = Real depth / Apparent depth
116
What is the critical angle?
The angle of incidence in the denser medium when the angle of refraction in the less dense medium is 90 degrees.
117
What happens when the angle of incidence exceeds the critical angle?
Total internal reflection occurs.
118
In total internal reflection
does light pass into the less dense medium?
119
What is the relationship between refractive index (n) and critical angle (C)?
n = 1 / sin C
120
What is a mirage?
An optical illusion caused by the refraction and total internal reflection of light in the atmosphere.
121
Why does a mirage occur on a hot road?
The air near the road is hotter and less dense
122
What is the shape of the cone in which a fish sees the world outside the water?
A cone of half angle 49 degrees (total angle 98 degrees).
123
What is the angle of incidence?
The angle which the incident ray makes with the normal to the surface at O.
124
What is the angle of refraction?
The angle between the refracted ray and the normal to the surface at O.
125
What is the angle of emergence?
The angle between the emergent ray RS and the normal at R.
126
When does the angle of refraction (r) become less than the angle of incidence (i)?
When light travels from a medium A to a more dense medium B.
127
When does the angle of refraction become more than the angle of incidence?
Conversely if light travels from a denser to a less dense medium.
128
In refraction through a rectangular glass block
how is the emergent ray related to the incident ray?
129
Does the speed of light change during refraction?
Yes.
130
What is the formula for refractive index in terms of real depth and apparent depth?
n = Real Depth / Apparent Depth
131
What causes the apparent depth of a river or swimming pool to be shallower than the real depth?
Refraction.
132
Why does a rod or spoon appear bent when partially immersed in water?
This is due to the fact that rays from different points of the object below the water surface are refracted away from the normal as they emerge from water to air.
133
What is refraction?
The abrupt change in the direction of light waves as they travel from one transparent medium to another of different density.
134
What causes refraction?
The difference in the speed of light in the different media.
135
State the laws governing refraction of light.
1. The incident ray
136
What is Snell's Law?
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media.
137
What is refractive index?
A number which gives a measure of refraction or bending of light as it travels from one medium to another.
138
How is refractive index related to the speed of light?
Refractive index = (speed of light in air (vacuum)) / (speed of light in glass).
139
What is the relationship between real depth and apparent depth?
n = Real Depth / Apparent Depth
140
What is total internal reflection?
The reflection of an incident ray of light at the interface between the medium of incidence and another medium of lower refractive index when the angle of incidence in the denser medium exceeds the critical angle.
141
What are the conditions for total internal reflection?
1. Light must be travelling from an optically more dense to an optically less dense medium. 2. The angle of incidence in the denser medium must be greater than the critical angle.
142
What is critical angle?
The angle of incidence in the denser medium when the angle of refraction in the less dense medium is 90 degrees.
143
How is refractive index (n) related to critical angle (C)?
Refractive index (n) = 1 / sin C
144
What is a mirage?
A natural effect due to total internal reflection occurring at the boundary of a hot and cooler air.
145
What happens to light rays as they pass through a triangular glass prism?
The emergent ray is not parallel to the incident ray
146
What is angle of deviation?
The angle between the incident ray and the emergent ray of light passing through a prism.
147
What factors determine the amount of deviation of light by a prism?
(a) the angle of incidence (b) the refracting angle (A) of the prism and (c) the refractive index of the material of the prism.
148
What is the relationship between refractive index (n)
refracting angle (A)
