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Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
1. How can you PROVE that light is a wave?
2. How can you PROVE that light is a particle?
3. What is the speed of light?
4. What variable do we use for the speed of light?
5. When energy goes into an atom is light produced?
6. What is the speed of radio waves with a wavelength of 4.2 m?
7. What do we call a prism spreading out light into its colors?
For all of the following conversions, use scientific notation. 8. Convert 400 nm to m.
9. Convert 90 MHz to Hz.
10. Find the frequency of light rays that are 650 nm long.
11. What do scientists call all light, both visible and invisible?
12. Which has higher frequency: red or blue light?
13. Which has a longer wavelength: red or blue light?
14. Three light bulbs are above a circle. A. If all of them are off, what color is the circle? B. What color if all are on? C. What color if B and R are on? D. Which have to be on to produce magenta? E. Which have to be on to produce green? F. Which have to be on to produce yellow? G. Which have to be on to produce black?
B G R
What color?
Light and Color Basics
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
15. Is the blocking tube adding or subtracting light?
16. Fill in the colors for the different regions and write RGB for each. Use a slash thru a letter to show a color that is missing. Ex: RGB means R and G are present, but B is blocked.
17. In CMYK, A. What is K? B. How do you make yellow? C. How would you make red? D. How would you make white?
18. White light shines onto a patch of magenta paint. A. What lights make up magenta? B. For you to see magenta, what lights must be reflected? C. What color must NOT be reflected? D. So, what color is absorbed by magenta?
19. What color is absorbed by cyan?
20. A blue filter is put in front of a red light. A. What color does it look like? B. Why?
21. A. The phosphorus pad (glow-in-the-dark) was what color? B. What color was it when blue light was shined on it? C. Why?
Magenta
White light
Light and Color Basicsp.2
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Reflection and Refraction Lab
Concave Mirror 2. A. Draw the light rays after they reflect.
B. Do the light rays converge or diverge?
C. If the rays converge, label the real focal point.
D. If the rays diverge, draw dotted lines backwards to the virtual focal point.
E. Which side of the mirror is real?
Convex Mirror 1. A. Draw the light rays after they reflect.
B. Do the light rays converge (come together) or diverge?
C. If the light rays converge, label the crossing point the real focal point.
D. If the light rays diverge, draw dotted lines back to where the rays seem to come from. Label it the virtual focal point.
E. When the light hits the mirror, the rays really reflect back to the left. So the left side of the mirror is real.
Convex Lens 3. A. Draw the light rays after they refract thru the lens.
B. Is this device convergent or divergent?
C. If the rays converge, label the real focal point.
D. If the rays diverge, draw dotted lines backwards to the virtual focal point.
E. Light really passes thru a lens, so the right side of a lens is real.
Concave Lens 4. A. Draw the light rays after they refract thru the lens.
B. Is this device convergent or divergent?
C. Label the real or virtual focal point.
D. Which side of the lens is real?
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Flat (Plane) Mirror 5. Change the light source so that it only has one ray projected. A. Draw the light rays path.
B. Label the ray that hits the mirror the incident ray.
C. Label the ray that reflects off the mirror the reflected ray.
D. The imaginary dotted line is perpendicular to the mirror. Label this line the normal. All angles must be measured from the normal.
E. How do the two angles compare?
Acrylic Block 6. Change the light source back to multiple ray projection. A. Draw the path of the light rays. If you cant see the rays inside the acrylic, then connect the lines from the right and left side to show the interior path.
B. What do we call the imaginary perpendicular line?
C. Which ray hits first: top or bottom?
D. Does the ray bend up or down?
7. Turn the acrylic block to the position shown at the left. A. Draw the path of the light rays.
B. Which ray hits first: top or bottom?
C. Does the ray bend up or down?
8. Turn the acrylic so that it is perpendicular to the light rays. A. Draw the path of the light rays.
B. Which ray hits first: top or bottom?
C. Does the ray bend up or down?
9. Acrylic and glass are denser than air, so light travels slower. This is why light bends or refracts. Which way will the following refract?
Glass
Air Glass
Air Glass
Air
Refraction and Reflection Labp.2
i
R Normal
Normal
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Optics Basics
Lenses Mirrors
The right side hits first it bends to the right.
Refraction Light refracts when passing between two substances at an angle. Reflection
GLASS
Light slows down in glass. If the left side hits first, it slows down first, causing it to bend to the left.
GLASS
Light speeds up in air. Here the left side speeds up first causing the light to bend to the right.
light ra
y
GLASS If the light
does not enter at an angle, it
does not bend.
Light reflects at shiny boundaries we call mirrors.
Normal an imaginary reference line perpendicular (90o) to a surface.
Angle of Incidence the angle between the incoming ray and the normal.
Angle of Reflection the angle between the outgoing ray and the normal.
MIRROR
normal (90o to mirror)
angle of incidence
angle of reflection
60o 60o
angle of incidence = angle of reflection
Lenses work by refraction.
A convex lens is convergent the light rays come together.
Concave or Convex?
Concave looks like the sides have caved in.
Convexthe middle is bigger than the ends.
Mirrors work by reflection.
Lenses and mirrors work opposite of each other. A concave lens is divergent; then a concave mirror is convergent.
Straight Lines
Mirrors and lenses can make things look bigger or smaller because our eyes always think that light comes from straight lines,
even if they have been refracted or reflected.
water
object image
air
Object vs. Image
The object is what you are looking at: the actual thing.
The image is what you think you see: the object enlarged, reduced, or moved .
Focal Point
focal point or focus
Every lens or mirror has a place where incoming parallel rays will meet. This is known as the focal point or focus.
The focal point is NOT where the
image is in focus (unless the object
is at infinity).
Real focal point: rays actually cross here.
A concave lens is divergent the light rays spread apart.
Virtual focal point: rays seem to diverge from here.
A convex mirror is divergent the light rays spread apart.
Virtual focal point: rays seem to diverge
from here.
A concave mirror is convergent the light rays come together.
Real focal point: rays actually cross here.
lens paper
Real image
bulb
Object Focal point
Real Images
Just because you can see an image does not mean it is real. In optics a real image
is defined as one that can be projected (onto a screen or paper). Real images are
always inverted (flipped) and can only occur past the focal point, when the light rays have crossed. Therefore, only con-vergent devices can produce real images!
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
The angle between the incident ray and reflected ray is 60o. What is the angle of reflection?
The angle of reflection is 40o. What is the angle of incidence?
1. Optics
2. Image
3. Object 4. Concave
5. Convex
6. Convergent
7. Divergent
A. The study of how light behaves.
B. A lens or mirror that is bigger in the middle.
C. Light rays that spread apart.
D. Produced by a lens or mirror.
E. Light rays that come together.
F. What you are actually looking at.
G. A lens or mirror that is bigger at the ends.
1. Normal
2. Mirror
3. Angle of incidence
4. Angle of reflection
5. Lens
6. Focus
A. A line drawn perpendicular to the surface of a mirror or lens.
B. An optical device uses refraction to bend light.
C. From the normal to the incoming ray.
D. From the normal to the outgoing ray.
E. Where all parallel rays converge.
F. An optical device that works by reflection.
You stand 2 feet in front of a mirror. How far away from you does your image in the mirror seem?
Convergent or Divergent? Concave lens? Convex mirror?
Concave mirror? Convex lens?
Real or Virtual focal point? Concave lens? Convex mirror?
Concave mirror? Convex lens?
Can produce a real image? Concave lens? Convex mirror?
Concave mirror? Convex lens?
What is a real image?
Will a real image ever occur with a divergent device?
Why or why not?
The graphic shows what you would see when looking at the object thru a lens. Is the image it real or virtual?
Why?
Why can we see virtual images?
The angle of incidence is: _____ The angle of reflection is:______ The normal is: ______________ The incident ray is: __________ The reflected ray is: __________
Mirror
A
B
C
D
E
G
F
H
Which letter shows where the incoming light ray will go?
a
b c
Which arrow shows the correct path of the light ray?
c
b a
Focal point
object
Draw where the rays will go and label the type of mirror.
lens object When you look into your bathroom mirror, are you upside down (inverted) or right side up (upright)?
Is this a real or virtual image? Why?
What is the focal length of a bathroom (flat) mirror?
Optics Basicsp.2
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Index of Refraction Lab
Light Source
Acrylic
Block
Refle
cted
ray
Outgoing ray
Incident (incoming) ray
A Outline block
B
D
C
Step 1 Lay out the acrylic block and light source as shown. The angle does not need to be the same, but it will make your measuring easier if you have a big angle between the incident ray and the block.
Step 2Draw an outline of the acrylic block (circle A below). For each of the three rays of light, make two dots (B-D below). You will use the dots draw the rays. This is more accu-rate than sketching.
Step 3With a ruler, use the dots to draw the three light rays. The rays stop when they hit the acrylic block. Dont make them too short, for you will use them later with a protractor to read angles. Give the lines arrows to show direction.
Step 4Draw the ray inside the acrylic by connecting the outside lines. This shows the path of the light inside the block.
Step 5With the exception of the dotted line and angles, your diagram should look very much like the one above. The dotted line is the normal an imaginary line perpendicular to the surface.
1
2
Normal
1
2
Norm
al
cstephenmurray.com Copyright 2009, C. Stephen Murray
Step 6 All calculations in optics require angles to be measured from the normal. Fortunately, protractors have a normal already on them. Just be sure to measure back from 90. Put a protractor on your dia-gram and measure the incoming angle (1) and refracted rays (2).
Step 7Calculate the index of refraction of acrylic using Snells Law: n1sin1 = n2sin2 , where the 1s mean the first substance (air) and the 2s mean the second substance (acrylic).
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Student Page:
Diagram:
Measurements:
n1 =
1 =
1 =
2 =
2 =
Calculation:
n1sin1 = n2sin2
Conclusion: nacrylic =
cstephenmurray.com Copyright 2009, C. Stephen Murray
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Refraction
When light passes at an angle into a medium of different speed it
refracts or bends. This is because in denser mediums, light bumps
into more particles, slowing down.
Snells Law
n1sin1 = n2sin2 Incident ray
(first substance) Refracted ray
(after) Glass
(before)
Air (after)
normal
1 = 30o
2 =
50o n2 = 1
n1 = 1.52
Example: Light traveling at 35 in air enters water. At what angle does it refract?
n1 = 1 (air) 1 = 35
n2 = 1.33 (water) 2 = ?
1 1 2 2
2
2
12
n sin = n sin 1(sin35) = 1.33(sin ).5736
= .4313 = sin1.33
sin (.4313) 25.5
= =
Critical Angle (C) When light passes from slow to fast medium, eventually light will refract at 90. This angle is called the critical angle: C. Past this angle light reflects back (total internal reflection).
Glass (before)
Air (after)
normal
i = 41o
41 is the critical angle for glass (see example).
R = 90o
The ray refracts at 90
Second medium
First medium
2C
1
nsin =
n (only if n1 > n2) n1 = 1.52 (from glass)
n2 = 1 (to air) C = ?
Example: What is the critical angle from glass to air?
2C
1
C
1C
nsin
n
1sin 0.658
1.52sin (0.658) 41
=
= =
= =
The index of refraction (n) tells you how much light slows down in a medium. Index of Refraction (n)
cn =
v
Speed of light in a vacuum (3 x 108 m/s)
Speed of light in any
substance (in m/s)
Index of refraction (no units)
As n increases, light moves slower and refracts more.
Vacuum n = 1
Air n = 1.000293
Ice n = 1.309
Water n = 1.33
Glass n = 1.52
Diamond n = 2.419 slow
er
faste
r
(just use 1)
c = 3 x 108 m/s nglass = 1.52 vglass = ____
8
8
cn
v
c 3 x 10v
n 1.52v 1.97 x 10 m / s
=
= =
=
Example: Find the speed of light in glass.
Snells Law allows you to calculate how much light will refract when it crosses a boundary.
ALL angles must be measured from the normal!
Just like a car entering a puddle of water, the side that enters first slows down and light bends that way.
air (fast) water (slow)
Rays that enter perpendicular to the surface (parallel to the normal) do not refract because both sides slow down at the same time.
air
water
normal
Glass Air fast
slow Even at extreme
angles, light refracts as it passes from
fast to slow.
There is NO CRITICAL ANGLE if light passes from a fast medium to a slow medium (if n1 is smaller). Glass
Air
normal
c
= 41o Less than c
Angles greater than
C reflect.
Angles less than
C refract.
At
C the light refracts at 90
More than c
Past the critical angle, light reflects.
Refraction
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
1. Index of refraction
2. Refraction
3. Critical angle
4. Snells Law
5. Normal
A. When light bends at a boundary due to a changing of lights speed.
B. Reference line for all angles.
C. Tells us how much light will refract in a substance.
D. n1sin1 = n2sin2
E. The angle past which light will reflect instead of refract.
6. c
7. n1
8. c
9. 2
10.n2
11.v
12.1
A. Angle of light in first substance.
B. Speed of light in a vacuum.
C. Critical angle for a substance.
D. Velocity of light in any substance.
E. Index of refraction for the second substance.
F. Angle of light in the second substance.
G. Index of refraction for the first substance.
13. Why does light bend as it passes into a new substance at an angle?
14. In which substance does light have a faster speed: air or water?
15. Which side of the car will get out of the water first?
16. Will that side speed up or slow down in air?
17. Draw the path light will follow.
18. Did it bend toward or away from the normal?
air
water A
B C D E
A B C D
E
water
air A B C D
E
water
air
A B
C air glass
air water
19. For each of the following situations, determine the path light will follow.
23. The diagram shows a ray of light refracting from air to water. Which number corresponds to: A. _____1 B.______normal C.______Surface of water D. _____Incident ray E.______2 F. ______Refracted ray
24. If the above incoming angle is 50, find the refracted angle.
20. Light travels at 2.06x108 m/s in quartz. Calculate the index of refraction for quartz.
21. Using the table on the front, calculate the speed of light in water.
22. Two substances: nA = 2.35; nB = 1.65. In which substance does light have the faster speed?
Air
Water
4 2
3
5 7
8 9
1 10
6
25. What is the critical angle from water to air?
26. Will the light refract or reflect? A. If the angle from water to air is smaller than c?
B. If the angle from water to air is greater than c?
27. Calculate the critical angle from air to water.
28. Will there be a critical angle for light as it passes to the new substance?
29. Why or why not?
n = 1.75
n = 1.15
Refractionp.2
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
Lens/Mirror Equation and Magnification
Real or Virtual
The direction light goes after hitting a mirror or lens is
the real side.
The right side of a lens is real, because light REALLY refracts thru lens.
Focal Length f
f is the focal length: the distance from the
mirror or lens and the focal point.
The left side of a mirror is real, because light REALLY reflects back from a mirror.
Divergent devices have virtual focal points, so f is .
Real focal point Virtual side Real side
Virtual focal
point.
Real side Virtual side
-f +f Convergent devices have real
focal points, so f is +.
Object and Image
The object is what we are looking at: the light source.
The image is what is reflected or
refracted by the device. We will always put the
object on the left.
Lens/Mirror Equation
1 1 1p q f
+ =Object
distance (in cm or m)
Lens and Mirror Equation
Image distance (in cm or m)
Focal length (in cm or m)
This equation lets you calculate p, q, or f knowing two of them. Use the above rules to be sure they have the correct signs (+ or ). NOTE:
You can use cm or m, but
not both! Example: The object is 30 cm to the left of a convex lens. The image comes into focus 20 cm to the right of the lens. Calculate the focal length.
p = 30 cm q = 20 cm (+ since on right side of lens) f = _____
1 1 1p q f
1 1 13 0 2 0 f
1.0 3 3 .0 5
f
+ =
+ =
+ =
1.083
f1f = 12cm
.083
=
=
And + means on the right side of a lens.
M is + if the image is virtual, upright, and on the virtual side.
M is if the image is real, inverted, and on the real side.
+p +q p = object distance. p is always +. q = image distance. q is + if on the real side
of the device OR if the image is inverted (real).
10
20 30 40 50 80 70 60 90
Object Real image Convex lens
+f +h
h = objects height. h is always +.
-h
h (h prime)= image height.
h is if inverted (real); h is + if upright.
Magnification
h' qM = h p
=
Magnification (no units)
Magnification
Object height (in cm or m)
Object distance (in cm or m)
Image height (in cm or m)
Image distance (in cm or m)
The magnification tells you if the image is larger or smaller, virtual or real.
1 cm 2 cm
Object Image Obviously the magnification here is 2, because the image is twice as big. It is +2 because
the image is upright and virtual.
Example: The object is 30 cm away from a convex mirror and 2 cm tall. The image seems to be 20 cm to the right of the mirror. Calculate the height of the image.
p = 30 cm h = 2 cm q = -20 cm (- since on right side of a mirror) h = ______
h' qh p
h' -202 30
=
=
h' +20 =
2 3040h' = 1.33cm30
=
Since h is +, the image is upright, which means it is virtual!
All real images are produced on the real side of the device. For all real images q is + and h is .
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
1. p
2. q
3. h
4. h
5. M
A. Magnification of the lens.
B. Height of the image.
C. Distance from lens or mirror to the image.
D. Distance from lens or mirror to object. E. Height of the object.
Which side of a lens is real? Why?
Which side of a mirror is real? Why?
When is f negative?
When is q negative?
When is p negative?
When is h negative?
When is h negative?
When is M negative?
The magnification of a convex mirror is 5. The object is 3 cm tall. How tall is the image?
Is the image real or virtual?
Is the image on the left or right side of the mirror?
The object is 12 cm from a convex lens that has a focal length of 5 cm. Is the lens convergent or divergent? Real or virtual focal point? Positive or negative focal length? Find the distance to the image.
Positive (+) or negative ()? A. _____ Object distance (p). B. _____ Right side of a mirror. C. _____ Left side of a lens. D. _____ f for divergent devices. E. _____ q for a real image. F. _____ Left side of a mirror. G. _____ h. H. _____ Right side of a lens. I. _____ f for convergent devices. J. _____ f for a convex mirror. K. _____ f for a concave lens. L. _____ q for a virtual object. M. _____ h for a real object.
Label the above diagram with p, q, h, and h. Be sure to mark them with + or .
Is the image real or virtual? Why?
Will the magnification be a positive or negative number?
Will the magnification be greater than or less than 1?
10
20 30 40 50 80 70 60 90
On the diagram, label p, q, f, h, and h.
Variables: p = q = f = ______
Calculate the focal length.
Calculate the magnification.
If the object is 1.5 cm tall, calculate h.
Lens Equation p.2
Name: _____________________
Period: _____________________
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Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
1. Place the lens at the center of the meter stick (at 50 cm), determine the focal length of the lens from p and q. A) Place the object someplace to the left of the lens (at least 20 cm away). B) p = _________ (from 50 cm to the object). C) Move the screen until the image is in focus. D) q = _________ (from 50 cm to the object). E) Calculate f, using the lens equation. f = _________
2. On two sticky notes, draw an f and an arrow. Place them a distance of f on both sides of the lens. Ex: if f = 10 cm, then put the notes at 40 cm and 60 cm.
3. The radius of curvature is twice the focal length. C = 2f. Put sticky notes a distance of C on both sides. Ex: if f = 10 cm, then C = 20 cm. Put the C sticky notes at 30 cm and 70 cm.
4. Q: If you move the object to the right (closer to the lens), which way does the image move? 5. Q: If you move the object to the left (farther from the lens), which way does the image move? 6. Q: To increase the size of the image, which way do you move the object? 7. Q: To decrease the size of the image, which way do you move the object? 8. Q: Which side of the lens is real? Why? 9. Fill in the following table. For each situation try to locate the image. If you cannot find the image,
try looking backwards thru the lens.
Situation p q f Upright or Inverted? Magnified or Reduced?
p is greater than C
p = C (put the object at C)
p is between C and f
p is at f
p is less than f
+p +q
p = object distance. p is always +. q = image distance. q is + if on the real side of the device OR if the image is inverted (real).
10
20 30 40 50 80 70 60 90
Object Real image (projected) Convex
lens
+f +h
h = objects height. h is always +.
-h
h (h prime)= image height.
h is if inverted (real); h is + if upright.
Convex Lens Lab
f C f C
Name: _____________________
Period: _____________________
cstephenmurray.com Copyright 2009, C. Stephen Murray
__________ Lens
Ray Diagrams
Ray diagrams are a way to visualize how mirrors and lenses work. If drawn precisely and to scale (with a ruler), a ray diagram can tell you exactly where the image is, whether it is real or virtual, and its size.
Ray 1 Ray 1 is horizontal and goes from the top of the object to the device. From the device it is drawn to the real focal point if convergent or from the virtual focal point if divergent.
Ray 2 Ray 2 starts at the top of the object and goes to the center of the device. Ray 2 continues thru a lens or reflects back from a mirror.
The Image If the rays converge, the top of the image is where rays 1 and 2 cross. If the rays diverge, draw them backwards (virtually). The virtual intersection is where the top of the image SEEMS to be.
Ray 1 starts horizontal and goes thru the correct focal point.
Convex lens: so +f
Ray 2 goes thru the center of the
lens and keeps going.
image
(real)
Convex Lens (convergent)
If the object is outside C (2f) in front of a convex lens, then the image is real, reduced,
and located between f and C.
Ray 1 starts horizontal and goes thru the correct focal point.
Ray 2 goes to the center of the
mirror and reflects back.
image
Convex mirror: so f (virtual)
Because the rays diverge, the image is at the intersection
of the two virtual rays.
Convex Mirror (divergent)
If the object is between f and C in front of a convex mirror, then the image is virtual,
reduced, and located inside f.
Radius of Curvature
A spherical mirror or lens is a portion of large sphere that has a
radius of C. C is always equal to 2f.
For all of the following diagrams: 1) label f and C on both sides of the device; 2) circle the correct focal point; 3) draw the ray diagram using the above rules.
__________ Lens
The intersection of the two rays is
the top of the image.
C f
C = 2f
Mirror with radius = to C
C C
f f C C f f
Name: _____________________
Period: _____________________
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__________ Mirror
__________ Lens
__________ Lens
__________ Mirror
__________ Mirror
Ray Diagramsp.2
Name: _____________________
Period: _____________________
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Miscellaneous Light Topics
Total Internal Reflection Fiber optics work by total internal reflection. Fiber Optics Light usually passes through clear boundaries, but if it strikes at an angle greater than the critical angle it will stay inside the medium (glass, air, etc.). Total internal reflection is when all the light is reflected back inside the medium. The critical angle for glass is about 41o.
Total Internal Reflection: light past the critical angle cannot escape.
glass tube
Fiber optics pass light through flexible glass or plastic tubes (called fibers). These tubes can be bent allowing light to be directed where it is wanted.
Fiber optic cables carry much of the worlds communications
(Internet and phone) because it travels at the speed of light.
Types of Lights Incandescent Light Fluorescent Light
Incandescent (normal) light bulbs make light by very high heat. The filament glows bright when enough electricity flows through it.
Incandescent light is very inefficient because most of the energy is lost as heat.
filament
Incandescent Light bulb
Fluorescent Light bulb
In fluorescent light bulbs electricity excites
a gas inside, emitting mostly UV light. The
white coating on the outside of the bulb
absorbs the UV light and emits white light.
Fluorescent lights are four times more efficient than incandescent bulbs.
3/4 of the energy of an incandescent bulb is lost to heat.
A laser gives off light of only one particular wavelength. Red lasers have a red beam, for example. This comes from forcing a substance (usually a gas) to give off light. This light bounces back and forth between mir-rors, causing other atoms to give off more light. When the light is powerful enough it escapes as a laser beam.
Photoluminescence Lasers
Glow-in-the-dark (photoluminescent) objects contain the element phosphorous. When phosphorous electrons are energized, they come down a few at a time, giving off light over time. When all the electrons have fallen the phosphorous goes dark. Visible light recharges them (raising them up) so that they give off light again.
Phosphorous atoms glow-in-the-dark
by giving off light gradually.
LASER Light Amplification by Stimulated Emission of Radiation
Laser light refracts, but does not spread out in a prism
because all of the light is of only one wavelength.
prism
cool
HOT
Polarization
Only light in one direction can get through a polarizer. Two polarizers turned 90o can cancel out all light.
normal light
polarizer
polarized light
2nd polarizer turned 90o
no light gets through 2nd
polarizer
Normal light is chaotic, with transverse waves moving in all directions. A polarizer allows only light going one direction to go through (like a comb).
Polarization is used in some sunglasses to
reduce glare.
Polarization is how some computers and most calcula-tors screens work..
Each polarizer allows light through. Two
perpendicular polarizers cancel out all light.
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A convex lens is convergent/divergent and magnifies/reduces. A concave lens is convergent/divergent and magnifies/reduces. A convex mirror is convergent/divergent and magnifies/reduces. A concave mirror is convergent/divergent and magnifies/reduces.
1. Total internal reflection
2. Critical angle
3. Fiber optics
4. Incandescent
5. Fluorescent
6. Filament
A. Light created from high heat.
B. The part of a light bulb that glows when hot and makes incandescent light.
C. When all light cannot escape glass or an-other medium and stays inside.
D. The angle past which light cannot escape.
E. Technology based on bending light in cables.
F. Efficient light from UV radiation.
1. Polarization
2. Polarizer
3. Photolumines-cence
4. Phosphorous
5. Laser
A. An object that screens out all but light in one direction.
B. Light amplification by stimulated emis-sions of radiation.
C. An element that releases light slowly; used in glow-in-the-dark objects.
D. The act of only allowing one-directional light to pass through a filter.
E. Objects that give off light slowly and to glow in-the-dark.
Show where the 3 light rays will go.
Concave or convex lens?
What do we call the dot?
Magnifying or reducing?
Convergent or divergent?
lens
Use RGB to make these colors.
Cyan ________ White _______ Green _______
Yellow _____ Black ______ Magenta_____
Use CMYK to make these colors.
Blue ________ White _______ Green _______
Red ________ Black _______ Magenta _____
How can light be redirected by fiber optics?
Can a fiber optic cable be bent any direction? Why or why not?
You have an office building and need to cut cost. What kind of lights will you use and why?
Light is passed through a polarizer. How could you cancel out light with a second polarizer?
What element is photoluminescent and why?
Why dont lasers spread out into a rainbow in a prism?
mirror
Show where the light will go. Concave or convex mirror?
Magnifying or reducing? Convergent or divergent?
Using CMYKWhat color does yellow absorb?
What colors does cyan reflect?
What has more energy: Radio waves or Visible light? What has a shorter wavelength: Ultraviolet or Gamma rays? What has a higher frequency: Visible light or Infrared?
If the angle of incidence is 25o, what is the angle of reflection?
If the angle between the incident and reflected rays is 80o, what is the angle of reflection?
If an image look 20 meters away in a mirror how far away is the object?
An object is 4 meters away from a mirror. How far away does the im-age look?
A sound wave has a period of 0.5 secs. Find its frequency.
Find the wavelength of the above wave.
If the fourth harmonic of a standing wave is 48 Hz, find the funda-mental frequency.
You hear your echo 6 seconds after you yell into a canyon. How wide is the canyon?
Angle of incidence: ______ Angle of reflection:_______ Normal: _______________ Incident ray: ____________ Reflected ray: ___________
Mi r ror
angle b
angle d
angle a
line a
line b
line c
angle c
Misc. Light Topicsp.2
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No Key at this time
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Lens
Mirror
1. A. Concave or convex? B. Convergent or divergent? C. Is f + or ? D. Draw the ray diagram. E. Is the image magnified or reduced? F. Is the image real or virtual?
2. A. Concave or convex? B. Convergent or divergent? C. Is f + or ? D. Draw the ray diagram. E. Is the image magnified or reduced? F. Is the image real or virtual?
6. Make the following additive colors using RGB.
Cyan _______
Red _______
White ________
Magenta ______
Yellow _______
Black ________
7. Make the following subtractive colors using CMYK.
Blue _______
Red _______
White ________
Magenta ______
Green _______
Black ________
8. A. What colors does Magenta reflect? B. What color does magenta absorb?
9. What color does Cyan absorb?
4. Where does light come from?
5. Why did the phosphorous pad (glow-in-the-dark) glow slime green regardless of the light that we shined on it?
3. Is light a wave or a particle? Prove your answer.
10. A. More energy: Microwaves or X-rays? B. Shorter wavelength: gamma rays or radio waves? C. Faster speed: green light or radio waves? D. Higher frequency: gamma rays or visible light? E. Less energy: red light or blue light?
11. Light is a transverse wave. Does light vibrate parallel or perpendicular to the motion of the wave?
12. As a wave, what moves thru the air as light travels: the air particles or the light energy?
13. If a light wave has a frequency of 1500 Hz, what is its period?
14. Find the wavelength of radio waves of 6.2 MHz.
15. Calculate the speed of 1,200 m microwaves.
16. If it takes the suns light 8 minutes to reach the earth, calcu-late the time it would take a satellite to send its radio signals back to NASA if it is the same distance from the earth as the sun.
Light and Optics In Class Review 1
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22. Why does light refract?
23. How can you decide which way light will refract?
24. Draw what will happen for the following situations.
18. Are the following + or ?
____ q if image is inverted. ____ h ____ h if the image is upright ____ M if the image is upright ____ h if the image is on the right side of a mirror ____ M if the image is virtual
____ q if the image is on the left side of a lens ____ h if the image is on the
right side of a lens. ____ q if the image is on the left
side of a mirror. ____ M if the image is real.
25. Find the speed of light in a diamond.
26. Light travels thru a substance at 1.6 x108 m/s. What is the index of refraction for this substance?
27. Two substances: A (n = 1.65); B (n = 2.44). A. In which substance will light travel slower? B. In which substance will light refract more from air?
20. A 4 cm object is in front of a convex mirror with a 3 cm focal length. The image is 2 cm to the right of the mirror. A) Is this mirror convergent or divergent? B) Is f + or for this mirror? C) Find where the object is.
D) Find the height of the image.
E) Find the magnification of the mirror.
F) Is the image real or virtual?
28. A ray of light is going 15 in water. At what angle will it be going when it passes into air?
29. Find the critical angle from a diamond to air.
30. The critical angle for a substance is 35. A. What happens at 32? B. What happens at 37?
5 4
6 1
7
8
9 3 2
A. The object: ____. B. Radius of curvature: ____. C. The focal point: ____.
D. q: ____.
E. p: ____.
F. f: ____.
G. The image: ____.
19. Identify the parts of the diagram above.
Convergent or
Divergent?
Magnifies or
Reduces?
+ or f?
Which side is real?
Concave Lens
Convex Lens
Concave Mirror
Convex Mirror
17. Fill in this table.
air
water
glass
air
diamond ice
air
glass
21. The object is placed between the focal length and center of curvature of a convex lens. A) Where will the image be?
B) Will the image be real or virtual?
C) Will the image be magnified or reduced?
In Class Review 1 - p.2
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1. A. For the diagram at the right what is the angle of reflection? B. What is the focal length of the mirror? C. Which is the real side of the mirror: top or bottom?
2. Find the critical angle for light passing from glass to water.
3. What is the speed of light in a cubic zirconium (n = 2.20)?
4. Why does light refract? (Be specific as to direction, too.)
5. Decide which way light will refract as it passes from the top medium into the bottom medium.
6. In example i, above, A. Which substance has a faster speed of light? B. Which substance has a higher frequency? C. Which substance has a longer wavelength for light?
7. Use the above setup to answer the following questions. This information was learned in the Convex Lens Lab. A. Label the object. B. Will the image be real or virtual? C. Will the image be magnified, reduced, or 1? D. Which way would you move the object to increase the size of the image? E. Draw where you think the image might be. F. Where would you put the object is you wanted a magnification of 1? G. Where would the image be if you put the object at f?
8. (From the July 2004 Exit Level TAKS test.) When trying to spear a fish in water, a person needs to take into account the way light bends as it moves from water into air. The bending of light as it passes from one medium into another is know as
mirror
30 60
Q1
lens
f C C f
i. ii.
Air
Glass
water
air
Light and Optics In Class Review 2
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In Class Light Review 2
70 80 50 60 40 20 30 10 90
Mirror
Light Source
Total internal reflection Photon Electromagnetic Spectrum
Polarizer Critical angle Laser
Fiber Optics Index of Refraction Dispersion
9. The above shows a light source creating an image on a piece of paper from a mirror. A. Mark p, q, h and h. B. What kind of mirror is it? C. Will the image be real or virtual? D. Why? E. Which is bigger p or q? F. So, without calculating, will the image be magnified or reduced? G. + or : p ____; q ____; f ____; h ____; h ____. H. Calculate the focal length and magnification of the lens.
10. Use this word bank for the following definitions. Words will be used more than once.
11. The diagram at the right shows light passing from air into a piece of glass. A. What is the incoming angle? B. Calculate the refracted angle (in the glass).
C. Draw the reflected light ray inside the glass block.
A. Includes radio waves, x-rays, and microwaves. B. Is the principle used by fiber optics. C. Two of these at right angles can cancel out light. D. If this number is bigger, the light refracts more. E. A single packet or particle of light. F. Angle at which light refracts at 90 to the surface. G. When white light separates into its different colors. H. A light source that has only one wavelength of light. I. Given off when the excited electrons in the atom fall to a lower orbit. J. A tube that can guide light, even around corners. K. Beyond this light reflects instead of refracts. L. Will not spread out when passed thru a prism. M. All light, both visible and invisible. N. If the incoming ray is within this amount light will refract thru. O. When light becomes trapped inside a substance. P. After passing thru one of these all of the light is in one direction. Q. Light amplification by stimulated emission of radiation. R. A number that tells you how slow light moves in a substance. S. What happens to white light when it passes thru a prism. T. Works by total internal reflection.
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lase
r
Diffraction gradient
Central Peak
(m = 0) First Max
(m = 1) First Max
(m = 1) Second
Max (m = 2)
Second Max
(m = 2) Second
min. First min.
First min.
Second min.
for m = 2
for m = 1
Piece of glass with vertical slits (cuts) in it.
d = distance between slits (in m)
Laser produces light of only one wavelength, .
wavelength (in m)
Brightest Dimmest
The bright spots are where
constructive interference
occurs (the maximums).
The dark areas are where destructive interference
occurs (the minimums).
For the minimums:
dsin = (m+)
(where m = 1,2,3,4)
For the maximums:
dsin = m
(where m = 1,2,3,4)
Diffraction gradients are the easiest way to see the wave nature of light. If light was only a particle it might bend a bit, but only a wave is able to interfere with itself: make constructive and destructive
interference. How astounding that two light rays can combine together to make darkness (minimums)!
Example 1: A diffraction gradient produces a pattern with 32 from the central peak to the
second maximum if 550 nm light is used. Find the distance between the slits.
-9
m = 2 (second max)
= 550 nm = 550 x 10 m
32 d ?
= =
-9
-9
-9
-6
d sin md sin 32 2(550 x 10 )d(.5299) = 1100 x 10
d 2076 x 10 m2.076 x 10 m
= =
=
=
Example 2: A diffraction gradient has 450 lines per mm. The first minimum is at 15.
Find the wavelength of the light used.
-3
-3
6
m = 1.5 (first min)450 lines = 1 x 10 m
1 x 10d 450
d 2.22 x 10 m15 = ?
=
=
=
-6
-7
-7
-7
d sin m(2.22 x 10 )sin15 1.5
5.74 x 10 = 1.55.74 x 10
1.5 3.8 x 10 m380 nm
= =
=
==
Diffraction Gradients
Dimmest