Optics Flashcards
(172 cards)
1
Q
What is refraction
A
the bending or changing of the direction of light when it travels from one medium to another
2
Q
Light travels at different
A
speeds in different materials
3
Q
Speed of light in a vacuum
A
3.00 * 10 ^8 m/s
4
Q
Speed of light in water
A
2.25*10^8 m/s
5
Q
Physicists can measure the
A
optical density of a material
6
Q
What is optical density
A
the ability of a meterial to slow down the movement of light
7
Q
The higher the optical density the
A
slower the movement of light and thus the more bent the light appears
8
Q
Is it possible for light to travel faster than it does in a vacuum
A
no! in a vaccuum light will move as fast as it can,
9
Q
Why does light move the fastest in a vaccuum
A
as there is nothing to slow it down
10
Q
When light travels from one medium it will
A
change direction and appear to bend
11
Q
Thus refraction occurs
A
as light crosses the boundary between two different materials
12
Q
When light moves from one medium into another of greater optical density the refracted ray will
A
bend towards the normal
(slowing down)
13
Q
When light moves from one medium into another of lower optical density the refracted ray will
A
bend away from the normal (speeding up
14
Q
when light moves from water to air it
A
bends away from the normal
15
Q
And image in water will appear
A
closert to the surface than the object
16
Q
Total internal reflection can occur when
A
light moves from a medium with greater optical density into a medium with lower optical density
17
Q
As light refracts some light will
A
also reflect back and follow the law of reflection
18
Q
As the angle of incidence increases, the intensity of light gets
A
weaker in therefracted ray and stronger in the reflected ray.
19
Q
The critical angle (OC) is the angle of incidence where the refracted ray is
A
directly on the boundary, 90 degrees to the normal
20
Q
At an angle of incidence
A
reater than the critical angle, light does not refract at all, and only reflects back into the initial medium
21
Q
The principle of total internal reflection is used in many places including
A
periscopes, binoculars, and retroreflection
22
Q
Diamonds are cut in specific ways to make use of what
A
total internal reflection
Total internal reflection makes them sparkle
23
Q
Fiber optic cables work because of
A
total internal reflection
24
Q
Light travels at different
A
speeds in different mateirials
25
Physcistits compare the speed of light in a vaccuum to the
speed of light in a particular medium,
26
The ratio comparing the speed of light in different materials is called
the index of refraction
27
The speed of light is different for each medium but is always
less than the speed of light in a vaccuum
28
You can determine the index of refraction (n) by doing what
dividing (C) speed of light by (v) speed of light in your materials
29
C and v are both speeds which means that n will have no
units, it is a dimensionless quantity
30
Where have you seen or used lenses
glasses, contacts, magnifying lenses, microscopes, telescopes, camera
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The eye also contains a lens which allows you to focus on objects
near and far
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Leses consist of two basic shapes
convex - converging
concave-diverging
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Convex lenses are thickes in the
middle
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lens CONVEX-light rays that are parrallel to the PA will
converge through a single point after they have been refracted
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CONVEX-The thicker the lens
the smaller the focal legnth
36
Concave lenses are thinnes in the
middle
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CONCAVE-light rays that are parrallel to the principal axis will
diverge as if they had come from a single point
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CONCAVE-The thicker the lens
the smaller the focal legnth
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There are always two
points of refraction in a lens
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The first point of refraction is
at the boundary between the air and glass
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the second point of refraction is
between the glass and the air
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we will simplify our diagrams by adding a
central line and only showingg light refracting once
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CONVEX: primary focus
light rays parrallell to the principal axis meet being refracted (F)
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CONVEX: secondary focus
located on the same side as the incident rays F'
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CONVEX: Twice the focal legnth is
2F 2F'
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CONVEX: Optical center is
(O) the middle of the lens and the point at which the principal axis meets the lens
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CONVEX: an incident ray that goes through F' will
refract parrallell to the principal axis
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CONVEX: an incident ray that goes through O will
continue on the same path
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CONVEX: an incident ray parrallell to PA will
refract through FA
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CONVEX: An incident ray passing through 2F' will
refract through 2F
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CONCAVE: what switches for concave lenses
F and F'
F is now on the incident side
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CONCAVE: An incident ray parrallel to the PA that meet the lens will
refract as if it came from the focal
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CONCAVE: an incident ray moving towayrds F' will
refract parrallell to PA
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CONCAVE: an incident ray that goes through O will
Continue
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LEns CONVEX: beyond 2F (SALT)
Smaller, Inverted, Between F and 2F, Real
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CONVEX: at 2F (SALT)
Same, Inverted, On 2F, real
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lens CONVEX: Between F and 2F
Larger, Inverted, Farther than 2F, Real
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CONVEX: At F
NO IMAGE
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CONVEX: Between F and O
Larger, Upright, Between F and lens, Virtual
60
CONCAVE: Beyond 2F
Smaller, Upright, Between F and the lens, virtual
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CONCAVE: At 2F
Smaller, Upright, Between F and the lens, virtual
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CONCAVE: Between F and O
Smaller, Upright, Between F and lens, Virtual
63
Equation to find the focal legnth
1/F (focal legnth) =
1/di
(distance from mirror lens to image, if negative image is virtual)
+ 1/do (distance from mirror lens to object)
64
WHat is magnification
the change in image size compared to the object
65
Give me the equation for M using height of image, and height of object
M (Magnification =
hi/ho
66
Give me the equation for m using distance of image and distance of object
M= -di/do
67
give me the equation for M using height of image, heigh of object, distance of image, and distance of object
M=hi/ho=-di/do
68
If the image height is - the image is
inverted
69
IF the image size is greater than the object the magnification will be
greater than 1
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IF the image size is smaller than the object the magnification will be
less than 1
71
Where is the optical nerve
behind the ey
72
What is the cornea
the very outer part of the front curve (looks like a contact)
73
What does the lens look like
a circle in the eye (inside)
74
What does the pupil look like
air bubble above the lens
75
The sclera is
the outer part of the rest of the eye
76
Choroid is
the first ring below the sclera
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The retina is
the second ring below the sclera
78
the fovea is
the bumpy part at the back
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The iris iss
the little bumps in the pupil
80
The ciliary body is
the part of the eye inside the sclera that doesn't have a retina or choroid
81
The entire eye is a focusing system that involves
the cornea, the lens, the retina
82
Good eyesight requires
precise focusing of light rays onto the retina
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The CORNEA
Outer layer of the eye,
made of living celss that are completely clear,
light arriving at the cornea is refracted through the pupil
84
THE LENS
the lens is convex
The focal legnth can be adjusted to meet different needs
The lens is attached to cilary body, which can contract or relax to alter the shape of the lens
85
When muscles in teh they eye contract the lens becomes
more spherical and thicker, to focus on nearby objects
86
When muscles in the eye relax the lens becomes
less spherical and thin to focus on distant objects
87
The RETINA
a layer of light sensitive tissue in the back of the eye
the light has already been focused by the cornea, pupil and lens
The image is formed inverted but the brain interprets the image as rightside up
88
3 categories of vision issues
Hyperopia (Far sighted)
Myopia (Near sighted)
Astigmatism (unable ot focus light rays)
89
Hyperopia
can focus on distant image, can't see nearby
Eye can't make the lens thick enough to foucs light on the retina, light is not refracted enough
90
Myopia
can focus on nearby objects and have difficulty focusing on distant objects,
the eye cannot make lens thin enough to focus light rays on the retina the light is refracted too much
91
Astigmatism
the eye is unable to focus light rays on the retina because of an irregualr shape of the cornea
92
Where's MY CAVE oh it's NEAR WE'RE IN FRONT OF IT
Myopia
Concave
nearsighted
light rays cross infront of the retina
93
Conduction
thermal energy can be transferred between molecules in direct contact with each other
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Heating up a pot or pan and the handles hot or place a spoon in tea and it gets hot is what
Conduction
95
Materials that aren't good conductors
WHat are they called
Plastic, wood
Heat can't travel easily
Insulators
96
What percent of the energy of sun is reflected back into space and by what
29
by clouds, particles in the atmosphere and the Earth's surface
97
what happens to the remaining 71% of energy from the sun
it is absorbed by earth's surface, clouds and gasses in the atmospher
98
Earth' warm surface emits
lower energy infrared radiation back out
99
The amount of energy radiated by earth's system is
equal to the amount of energy earth's system absorbs by the sun
Since these energy amounts are balanced Earth's global temp stays fairly consistent
100
Albedo is
the relative amount of the sun's energy reflected by a surface
101
Albedo warming
albedo decreases as ice melts-water absorbs more heat-arctic gets warmer-ice melts
102
Albedo cooling
albedo increases-ice reflects more heat-arctic cools-ice forms
103
What is a low albedo substance
water
104
what is a high albedo substance
snow
105
SOup on stove spoon gets hot, what is this
conduction
106
Heater warms the pool
convection
107
warm day bench at park is warm
radiation
108
bbq you feel hot
radiation
109
Why can't conduction and convection occur in space
Heat conduction and convection do not occur in space since there is no air in space. Heat transfers in space, which is a vacuum, only by radiation.
110
Does warm water rise or fall in cold water
Rise. This is because the warm water is less dense and it floats on the cold water – in the same way that a cork floats because it is less dense than water.
111
Why doesn't convection occur in solids
Convection is not possible in solids because for convection to take place the molecules of a substance should be free to move like liquids and gases. The molecules of a solid are tightly packed together, thus making it difficult for molecules to move around for convection to take place.
112
We can see our surroundings because
light bounces off of objects and into our eyes
113
the electromagnetic spectrum is made up of
different sized wavelegnth
114
Humans or only able to the see the
visible portion of the EM spectrum
115
The shortest wavelegnths are, the longest are
gamma waves, radio waves
116
all of the different wavelengnths combine together to
form a continuous spectrum
117
what is our most abundant light source
the sun
118
How does the sun make light
when energetic hydrogen atoms at the center of the sun collide they sometimes combine or fuse to form helium. These reactions are called fusion reactions. SOme of the energy produced by fusion is emitted as light
119
white light
most sources emit white light. White light is a combination of all wavelegnths of light. When light passes through a prism it is dividied into specific wavelegnths (colours)
120
rods
sensitive to dark changes shape and movement they are not effective at deticting colour
121
cones
used for colour vision and are wavelegnth specific
122
red cones
detecets long wavelegnths (red, orange, yellow)
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green cones
detects medium wavelegnths, (yellow, green, blue)
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blue cones
detects short wavelegnths (blue vilet)
125
when is a person colourblind
when one or more types of their cones are partially or completely defficient
126
dog vision
dogs have 2 types of cones (can't see red, orange and some yellow)
127
bee and butterfly vision
better vision able to see colours that we can't, can see in to the ultraviolet region
128
Incandescence
energy in-energy out (light. Something gets really hot and releases energy as light.
Examples: heating up a strucutre and it glows red. Incandescent light bulb filaments get really hot and glow bright white
129
electric discharge
electric current through a gas. the gas releases the energy as light.
Examples: neon signs, lighting
130
phosphorescence
materirals absorb UV energy and release the energy over a long period of time.
Example: Glow in the dark
131
fluorescence
materirals absorb UV energy and release the energy immediately as visible light.
Example: Fluorescent bulb, comact fluorescent bulb, detergents
132
chimluminescence
light from chemical reaction , example: glowsticks, luminol
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bioluminescence
light produced by chemical reactions within living things.
Examples: jellyfish, algae, fireflies, angler fish
134
triboluminescence
light produced from hitting or sticking rocks or crystales (friction)
example: flint, flint lighters
135
LED (light emitting diodes)
electricity passes through specific materials (semiconductors like silicon or galium), that release particular wavelegths of light
Examples: phone screens, computer screens, TVs, anything with red, green blue
136
light travels in
straight lines
137
lights straight lines are represented by
rays which show direction that light travels after it leaves its source
138
rays
each ray ends with an arrow, to indicate the direction of travel. IF more rays reach your eye the brighter the object appears
139
rays leaving the source
travelling toward an object travel closely to one another
140
the science of how light reflects and bends is called
geometric optics
141
angle of incidence =
angle of relflection
142
images are formed in the location wher
the relfelcted light rays cross. Therefore when your eyes detereflected light from a plane mirror, your brain projects these light rays backwards in a straight line. Your brain perceives a light source behind the mirror and that this source is where the light rays originate. this type of image is called a virtual image
143
a virual image is
an image formed by light coming from an apparent light source behind the mirror. the reflected light rays from a plane mirror will nvever cross in front of the mirror. However if the reflected light rays are extended behind the mirror the rays will appear to cross. this is where the image is found
144
SALT
Size of Image: comparison to object
Altitude of Image: image orientation compared to object
Location of image: point where reflected rays cross or appear to cross, how far from the mirror the image is compared to object
Type of Image: a real image or virtual
145
two characteristics of plane mirrors
virtual images, angile i= angle r
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angle of incidence
angle where ray hits mirror
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angle of reflection
angle leaving mirror
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incident ray
ray of light going towards mirror
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normal
perpendicualr line from mirror
150
reflected ray
light ray reflected from mirror
151
Curved mirror
depending on whether the reflective coating is on the inside or outside of the curve will decide if its a concave or convex mirror.
If coated on inside its concave
if coated on outside convex
152
circle terminology for mirrors
a curved mirror is a cut out section of a circle. IN mah the distance from the curve to the centre of the circle is referred as the radius. for the purpose of mirrors this called the center of urvature
153
principal axis
a line through the cneter of the of curvature that strikes the mirror at a 90 degree angle
154
vertex
point of a curve mirror wher PA meets mirror
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the center of curvature and vertex are on
the principal axis
156
half of the distance between the centre of curvature and mirros is
focus or focal point. this is why focus is F and center of curvature is 2F
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Concave: when incident ray goes through the center of curvature the reflected ray will
reflect back on itself
158
Concave: incident ray parallel to pa will
reflect through focal point
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Concave: incident ray passing through focus will
reflect parallel to PA
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Convex: Parallele to Pa
reflect from focal
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convex: passing through focus
reflect Parallelt to PA
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convex: trhough center of curvature
back on itself
163
concave beyond C
smaller, upside down, closer, real
164
165
concave at c
similar size, upside down, at c real
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concave vetween f and c
larger, upside down, on c, real
167
concave at f
wont reflect
168
concave between f and the mirror
larger upright further virtual
169
convex far from mirror
smaller, right side up, closer (f and mirror), virtual
170
convex closer to mirror
smaller, upright, between mirror and f, virtual
171
convex closest to mirror
smaller upright, between mirror and f, virtual
172
