Unit 3 Flashcards
1
Q
What does color depend on?
A
Light of a particular frequency being reflected from a surface or transmitted through a source
2
Q
why is light an EM wave?
A
because it does not need a medium through which to travel. it does travel through mediums.
3
Q
why are mirrors the best example of a nearly perfect reflection?
A
almost all of the light that reaches a mirror is reflected
4
Q
why do rough surfaces not reflect light as well as smooth surfaces?
A
because they reflect light in many directions at once
5
Q
what are two results of refraction of light?
A
dispersion and total internal reflection
6
Q
what happens to light that travels through a medium other than a vacuum
A
absorbed and re-emitted by particles within that medium. The more interactions the light has, the more it slows down and is bent.
7
Q
total internal reflection
A
the complete reflection of light back into its original medium
8
Q
when waves interact with matter, they can be…
A
reflected, transmitted, or a combination of both.
-Waves that are transmitted can be refracted.
9
Q
When a wave reaches a boundary between two media, usually…
A
some or all of the wave bounces back into the first medium.
10
Q
reflection
A
the return of a wave back into its original medium
11
Q
normal
A
incident rays and reflected rays make equal angles with a line perpendicular to the surface
12
Q
angle of incidence
A
the angle between the incident ray and the normal
13
Q
angle of reflection
A
angle between the reflected ray and the normal
14
Q
law of reflection
A
- states that the angle of incidence = the angle of reflection
- applies to both partially reflected and totally reflected waves
15
Q
virtual image
A
- an image that appears to be in a location where light does not reach.
- Plane mirrors produce only virtual images
16
Q
diffuse reflection
A
the reflection of light from a rough surface
17
Q
what happens to sound energy that is not reflected?
A
it is absorbed or transmitted
18
Q
reverberations
A
multiple reflections of sound waves
19
Q
what happens when a wave that is traveling at an angle changes its speed upon crossing a boundary between two media?
A
it bends
20
Q
refraction
A
the bending of a wave as it crosses the boundary between two media at an angle
21
Q
when are sound waves refracted?
A
when parts of a wave front travel at different speeds
-can happen in uneven winds or when sound is traveling through air of uneven temperature
22
Q
what causes refraction?
A
- changes in the speed of light as it passes from one medium to another
- or variations in the temperatures and densities of the same medium
23
Q
mirage
A
appearance of a distorted image. causes by the refraction of light in Earth’s atmosphere.
24
Q
since different frequencies of light travel at different speeds in transparent materials, they will refract…
A
differently and bend at different angles
25
dispersion
separation of light into colors arranged according to their frequency
26
what is needed to see a rainbow?
- sun must be shining in one part of the sky
| - water droplets in a cloud or in falling rain must be in the opposite part of the sky.
27
critical angle
the angle of incidence that results in the light being refracted at an angle of 90 degrees with respect to the normal
28
when does total internal reflection occur?
when the angle of incidence is larger than the critical angle
29
optical fibers
transparent fibers that pipe light from one place to another
30
for a reflection in a plane mirror...
- object size = object distance
| - object distance = image distance
31
in what way does the law of reflection hold for curved mirrors?
the sizes and distances of object and image are no longer equal
32
virtual image formed by convex mirror
smaller and closer to the mirror than object is
33
virtual image formed by concave mirror
can be larger and more distant than the object
34
what is meant by the idea that a surface may be polished for some waves and rough for others?
the surface is considered polished if differences in elevations in a surface are small (less than 1/8 of the wavelength of light that falls)
35
echo
reflected sound
36
wave front
the crest, trough, or any continuous portion of a 2D or 3D wave in which the vibrations are all the same way at the same time.
37
Explain how diffuse reflection allows us to see everyday objects.
- When light is reflected from a rough surface, rays travel along many different paths.
- Any path that a ray travels along is a path along which the object can be seen.
38
Explain how fiber optics works.
Light is passed through a cable made of glass.
- All the light it reflected back into the glass so none is lost as it travels along the cable.
- The light is coded with information.
39
Why is it incorrect to say that a material will be either reflective or refractive but not both?
Some materials, like water and glass reflect some of the light and refract the rest. Even light hitting a pane of glass straight on is reflected about 4% while about 96% passes through.
40
What happens to the energy of a light ray that is reflected?
The energy is reflected along with the light.
41
In transparent materials, why does blue light refract at greater angles than red light?
Blue light interacts more with the particles in the medium because its frequency is closer to the natural frequency of the particles. This causes it to refract at greater angles.
42
lens
piece of transparent material that refracts light.
43
converging/convex lens
thicker in the middle, causing rays of light that are initially parallel to meet at the focal point.
-forms either a real or virtual image
44
diverging/concave lens
thinner in the middle, causing rays of light to appear to originate from a single point
-always forms a virtual image
45
principal axis of a lens
the line joining the centers of curvature of its surfaces
46
focal point for a converging lens
point at which a beam of light parallel to the principal axis converges
47
focal plane
a plane perpendicular to the principal axis that passes through either focal point of a lens
48
focal length of a converging or diverging lens
the distance between the center of the lens and its focal point.
49
What does the type of image formed by a lens depend on?
- the shape of the lens
- the position of the object
- the distance between the lens and the object
50
real image
an image formed by converging light.
51
upside down/inverted image
a real image formed by a single converging lens
52
what are used to construct a ray diagram?
- the size and location of the object
- its distance from the center of the lens
- the focal length of the lens
53
three rays useful for the construction of a ray diagram
1. a ray parallel to the principal axis that passes through the focal point on the opposite side
2. a ray passing through the center of the lens that is undeflected
3. a ray through the focal point in front of the lens that emerges parallel to the principal axis after refraction by the lens
54
main parts of the eye
cornea: transparent, protective covering.
iris: regulates the amount of light entering the eye.
pupil: is the opening in the iris through which light passes.
retina: is the light sensitive tissue at the back of the eye.
55
three common vision problems
farsightedness, nearsightedness, astigmatism
56
farsighted
eyeball too short or cornea is too flat
57
nearsighted
eyeball too long or the surface of the cornea is too curved
58
astigmatism
a defect that results when the cornea is curved more in one direction than the other
59
aberrations
distortions of an image. two types: spherical and chromatic
60
spherical aberration
results when light passes through the edges of a lens and focuses at a slightly different place from light passing through the center of the lens
61
chromatic aberration
result of different speeds of light of various colors
62
how does a lens form an image?
by bending rays of light that pass through it
63
What condition must exist for a converging lens to produce a virtual image?
The object must be between the lens and its focal point.
64
Huygen's Principle
- light waves spreading out from a point source may be regarded as the overlapping of tiny secondary wavelets
- every point on any wave front may be regarded as a new point source of secondary waves
65
diffraction
any bending of a wave by means other than reflection or refraction
66
what does the extent of diffraction depends on?
the relative size of the wavelength compared with the size of the obstruction that casts the shadow
67
within an interference pattern, wave amplitudes may be...
increased, decreased, or neutralized
68
monochromatic light
light of a single color
69
diffraction grating
a multitude of closely spaced parallel slits
70
what are the colors seen in thin films produced by?
the interference in the films of light waves of mixed frequencies
71
iridescence
phenomenon in which the interference of light waves of mixed frequencies produces a spectrum of colors
72
incoherent light
the crests and troughs of the light waves don't line up with one another
73
coherent
a beam of light that has the same frequency, phase, and direction
74
when is laser light emitted?
when excited atoms of a solid, liquid, or gas are stimulated to emit photons in phase
75
hologram
a three-dimensional version of a photograph that contains the whole message or entire picture in every portion of its surface
76
how is a hologram produced?
by the interference between two laser light beams on photographic film
77
Interferometer
- Device that uses the interference of light waves to measure very small distances with high accuracy.
- Michelson and Morley used this device in their famous experiments with light.
78
when is a wave said to be refracted
when a wave reaches a boundary between two media and is transmitted through the second medium at a different angle and speed.
79
where should you place an object in front of a diverging lens in order to form a virtual image?
anywhere
80
distinguish between a virtual and a real image
Only a real image can be projected onto a screen.
81
what types of images are formed by converging lenses?
can form either real or virtual images depending on where the object is with respect to the focal point
82
what types of images are formed by diverging lenses?
always form virtual images that are smaller and are right side up.
83
Diffraction occurs when waves pass through a narrow opening. How does the diffraction change as the slit is narrowed?
increases as the slit is narrowed.
84
How does diffraction affect radio reception?
helps radio reception because radio waves bend around objects and reach areas that are not directly in the "line of sight."
85
What does diffraction depend on?
the wavelength and the size of the object.
86
List the key components and functions of a laser.
monochromatic light that is in the same direction and in phase.
This is produced via a) an excitable material, b) a source of energy to excite the material, and c) one photon stimulating the emission of another photon of the same frequency and phase.
87
If you increase the wavelength of light shining through a single slit aperture, what happens to the interference pattern formed?
becomes more spread out as longer wavelengths diffract more than shorter wavelengths.
88
what happens when light is incident on a rough surface
it is reflected in many directions
89
what causes the dispersion of light
different speeds of different components of light
