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Physics Exam 1 Review

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Wavelength of an x-ray?
1A
Ultraviolet (uv) wavelength
100A--4000 A
Visible light wavelength
Blue--4000A
Green--5500A
Red--7000A
What is below visible light
Infrared-->7000A
The wavelength of microwaves
Approx. 1cm
Wavelength of a radio wave
300 meters
What has the highest frequency but the shortest wavelength?
Gamma rays--Less than 1A
The relationship between wavelengths and frequency is:
Inverse
C=
Speed of light--300,000 Km/s
Speed of light slows down the most in what substance?
Diamond
Speed of light slows down to .75 in:
Water
1A =
The size of an atom
Speed of light slows down the least in:
Water
What slows light down the most?
Diamond
Why does light slow down in substances?
Absorption and re-emission
Glass blocks most of what kind of light?
Ultraviolet and infrared
Umbra
Shadow; complete darkness; can't see the light source
Penumbra
Gray; can see light source
If you are in the penumbra you see:
The partial eclipse of the moon.
If are in the umbra you see:
Total eclipse
The phase of the moon in total solar eclipse?
New moon
Path of totality:
The path of the tip of the umbra
How wide is the path of totality?
200 km wide
How big is the penumbra?
Size of a continent
During a solar eclipse the last glow before total darkness
"Diamond ring" "Corona"
At totality the moon does what?
Covers the sun completely
Corona
The white crown glow in the outer atmosphere
Prominences
Red/orange/pink see during solar eclipse
Solar eclipse
Shadow of the moon falls on earth
(sun moon earth)
Lunar eclipse
The moon passes into the shadow of earth
(sun earth moon)
Which eclipse harmful to the eye?
Solar eclipse
Why is a lunar eclipse safe to view?
You are looking at a very dark moon.
What kind of eclipse is more commonly seen?
Lunar
The stage of moon during total lunar eclipse?
Full moon
How many people can see a lunar eclipse?
Half of earth
What happens during a lunar eclipse?
The moon passes through earths shadow.
Rods do what?
Peripheral vision
Detect motion
Gray scale
Cones do what?
In the fovea (center)
Good at sharp detail
See color
What is needed to fire the cones?
A certain amount of light.
Averted vision:
Use rods
Low light levels
Look away purposely so you can see object clearly in peripheral vision
Virtual image
Where final rays appear to come from.
If person stands 5 feet from mirror, their image is:
5 feet behind mirror--10 feet away total
If a light ray goes from air to glass, or air to water it bends:
TOWARD NORMAL
Refraction
A bending of light caused by change of speed as light passes from one medium to another.
Normal
Perpendicular to surface
Refraction and bending cause a:
Slowing down of light. And vice versa.
Dispersion
Separation into colors
What color of light slows down the most?
Blue
(bends more)
Which direction does light bend when going through glass from air?
Toward the normal
Anti-sun, or anti-solar direction:
Shadow of your head (eyes)
In the Primary rainbow, what color is closest to the anti-sun?
Blue
In the secondary rainbow what color is closest to the anti-sun?
Red
Diffuse white glow is seen:
Beyond the blue band in the secondary bow
Under the blue in primary bow
Angle of secondary bow:
51 degrees
Angle of primary bow:
42 degrees
Alexanders dark glow appears:
Between the two bows
Why is the secondary bow fainter?
It has an extra loss at the second refraction
(2 losses)
Light from air to water bends:
Toward the normal
Light from water to air bends:
Away from the normal
How many times does a secondary bow bend (refract)?
2
When can you see a primary bow?
Late afternoon
Early morning
The sun must be within 42* of the horizon
Lunar rainbows can seen:
During or near a full moon
If a light ray goes from water to air, or from glass to air, ray bends:
AWAY FROM NORMAL
Refraction, Bending
Light Slows down!
Which color slows more than red?
Blue
Which color bends more than red?
Blue
Dispersion
Separation into colors
Your shadow is the:
Anti-sun, or anti-solar direction
Angle of first (primary) rainbow?
42 degrees
Angle of secondary bow?
51 Degrees
Above secondary rainbow?
Diffuse white glow
In between rainbows?
Alexander's dark band
Below primary rainbow?
Diffuse white glow
In primary bow, each color has:
2 Refractions, 1 reflection
In secondary bow, each color has:
2 refractions, 2 reflections
When can you see a primary rainbow?
Late afternoon or early morning
Why can you only see a primary rainbow in late afternoon or early morning?
Sun must be within 42 degrees of horizon
Why is the secondary rainbow more faint than the primary?
Extra loss at 2nd reflection
When are moonbows the best?
Near full moon
What are the degrees or moonbows?
42 degrees, and 51 degrees
What colors do lunar rainbows appear to be?
Grey, White, Silvery
What part of your eye sees moonbows?
Rods (They see low light and grey scale)
Light travels faster in ___________ air
thinner
Light travels slower in ________ air
denser
At sunset, the image of the sun is raised by:
1/2 degree
"Flattened sun"
Bottom of sun raised more than top
Actual sun sets about ___ minutes before image of sun
3 minutes
The hot road mirage is caused by:
Refraction: Light travels through thinner air, bounces off of hot road, and comes up through thicker air
Critical Angle in water:
48 degrees--100% reflected light
What looks like blue water on road is actually:
Blue sky
Critical angle in diamond:
25%
If angle of incidence is less than critical angle, than:
Some light escapes!
If: Angle of incidence is greater than critical, Then:
100% of light is internally reflected!
Prism (glass)
Total internal reflection
Fiber optics (light pipes) (optical fiber)
199% light transmission--total internal reflection
Diamond (Critical angle of 25 degrees)
Total internal reflection--Light trapped and reflected inside diamond dispersion (of colors)
Powers of CONVERGING diopters:
+2, +1
Powers of DIVERGING diopters:
0, -1, -2
Diopters of a normal "relaxed" eye. Used for looking at distant objects, like a mountain
+60
Diopters of a "strained" eye....for reading fine print
+64
+60 = power =1/f
f = 1/60m
Myopia
Near-sighted eye--cannot focus on distant objects--eye lens too strong
Cure for myopia (near-nearsightedness)
Diverging glasses...ex. -2 diopters diverging lens
Hypermetropia or Hyperopia
Far-sighted eye---cannot focus on nearby objects--eye lens not strong enough
Cure for hyperopia (farsightedness)?
CONVERGING glasses. Ex. +3 diopters converging lens
Presbyopia
Loss of sight with aging
Diopters in average adult?
60-64
Diopters in grandparents eye?
60-61
Cure for Presbyopia (old)?
Bi-focals! Glasses with +0 on top and +3 on bottom
What color of visible light has the lowest frequency?
Red
Which color of visible light has the highest frequency?
Blue
What is the fate of UV light that is cast on to glass?
It will not go through.
What happens to visible light that is incident upon glass?
It passes through easily.
Penumbra
Partially Blocked
Umbra
Completely blocked
Do Earth and Moon always cast shadows?
Yes
Rods
Located on edge of eye
see black and white
Detect motion
Used in dark
Cones
Located in fovea (center)
see color
Detect fine print
Need bright lights
What has the longest wavelength?
Radio
Which has the shortest wavelength? UV or IR?
Ultraviolet
Which has a higher frequency? UV or IR?
Ultraviolet
Is the speed of light independent of frequency?
Yes, all light travels at the same speed.
You can get sunburn on a cloudy day, but you can't get sunburn on a sunny day if you are behind glass. Explain
UV in blocked by glass but not by clouds
Suppose that sunlight falls both on a pair of reading glasses on a pair of dark sunglasses. Which pair of glasses would you expect to become warmer?
Dark absorbs light and gets warmer
Why does a high-flying airplane cast little or no shadow on the ground below while a low-flying airplane casts a sharp shadow?
Low flying plane the umbra reaches the ground, high plane umbra doesn't.
Why do object illuminated by moonlight lack color?
In the dark you use your rods and rods only see black and white
Why do we not see color at the periphery of our vision?
Rods are peripheral and rods cannot see black and white
In which medium does light travel faster, in thin air or in dense air? What does this difference in speed have to do with the length of a day?
Light travels faster in thin air, making the day 6 minutes longer
Is a mirage the result of reflection or refraction?
Refraction, mirage caused by hot and thin air on the road allowing light to move faster and bend.
Does a single raindrop illuminated by sunlight deflect light of a single color or does it disperse a spectrum of colors?
All colors
Does a viewer see a single color or a spectrum of colors coming from a single faraway drop?
One color
Which kind of road surface is easier to see when driving at night- a pebbled, uneven surface or a mirror-smooth surface?
Rocky road because it reflects more light back to the eye.
And why is it difficult to see the roadway in front of you when driving on a rainy night?
Rainy night- water reflects light and diffuses reflection
What is the minimum length of a plane mirror in order for you to see a full image of yourself?
Half of your height
If while standing on a bank you wish to spear a fish beneath the water surface in front of you, should you aim above, below or directly at the observed fish to make a direct hit?
-Below because of refraction the speed of light is slower in water.
If instead you zap the fish with a laser, should you aim above below or directly at the observed fish?
-Directly at it, the water will bend the light aiming it at the fish because of refraction
If the fish in the previous question were small and blue and your laser light were red, what corrections should you make?
Blue light bends more; the laser would miss, thus you need to aim below the fish.
A rainbow viewed from an airplane may form a complete circle. Where will the shadow of the airplane appear? Explain.
Right at the center of the rainbow. The point of the plane is the anti-sun.
Suppose you walk toward a mirror at 2 m/s. How fast do you and your image approach each other?
4 m/s, as both of you are travelling at 2 m/s.
A butterfly at eye level is 20 cm in front of a plane mirror. You are behind the butterfly, 50 cm from the mirror. How far away are you from the butterfly in the virtual image?
50cm from you to mirror, 20cm from mirror to virtual butterfly. Thus, 70cm.
Electromagnetic spectrum from shortest wavelength to longest:
Gamma rays
x-rays
Ultraviolet rays
Blue
Green
Red
Infrared
Microwave
Radio
Electromagnetic waves with wavelengths of 300 meters are called:
AM radio waves
The constantly moving bright and dark areas at the bottom of a swimming pool are caused by:
Refraction
Electromagnetic waves with wavelength of 7000 angstroms are:
Red and visible to your eye
What has the lowest frequency?
Radio waves
The moonbow looks grey or silvery to most people, and objects seen by moonlight usually are not colored because moonlight:
Is too dim to activate the eye's cones, so rods are used
Correct property of the eye's cones?
Concentrated near center of eye and detect color
Correct property of the eye's rods?
Found mainly around periphery of vision and used to detect motion
If a total solar eclipse occurs, then we know that
The umbra of the moon is touching the earth. (Sun>Earth>Moon)
What must be the phase of the moon on the day of a lunar eclipse?
Full moon.
Phase of the moon during a solar eclipse?
New moon
Who can see a total lunar eclipse?
Anyone on the half of the Earth toward the moon
"Prominencies" are:
Red/Orange in color and can be seen during a total solar eclipse
What is the minimum size of a plane (flat) mirror, so that children who are four feet tall can see their full height in the mirror?
2 feet tall
Atmospheric refraction makes the daylight hours
Longer than they would be otherwise
A hot road mirage is caused by
refraction
If you stand next to a swimming pool and lok down into the water, the image that you see of the fish swimming in the pool appears to your eye to be:
shallower than the actual fish
A primary rainbow is brighter than a secondary rainbow because:
Loos of light when the secondary has an extra reflection inside the drops
In a rainbow display, one of the places where we see a diffuse white glow is:
Next to the blue/violet bands of the primary bow
In a rainbow display, what colors do we see immediately next to Alexander's dark band?
Red on both sides from both rainbows
In making the secondary rainbow, each light ray does what in passing through a raindrop?
2 reflections, 2 refractions
When seen from an airplane, a rainbow can form a complete circle. The plane's shadow is:
In the center of the rainbow
If you see the primary rainbow in the sky, the sun must be:
Within 42 degrees of the horizon
If you view a rainbow just before the sun sets in the west, then you must be looking generally:
East
Examples of thins that are caused because light can refract (bend)
-mirages
-rainbows
-flattening of the sun
If you were to spear a fish by throwing a regular (metal) spear, you should aim:
Below the observed fish
If you wish to illuminate a red fish with a blue laser beam, you should aim your laser beam where?
Slightly above the observed fish
When passing from air through a glass prism and back out into air...:
Blue bends more than red, since blue travels slower than red does in glass
As you look at a setting sun, where would you point to show the direction of the actual sun?
About one solar diameter below the visible sun
The desert mirage, or hot road mirage, is related to?
A layer of cooler air over a layer of hotter air, and that light travels slower in cooler air
When a ray of light passes from water out into the air, the ray is bent
Away from the normal
If all colors slowed down in glass, but all colors traveled at the same speed in glass, then a beam of white light would strike a prism, pass through, and emerge on the far side as:
Bent, but not spread into colors
When you watch a movie at a theater, the image on the screen is, technically,:
An upside down image of the film frame
A scuba diver shines a light beam up towards the surface of a smooth pond at a 10 degree angle to the normal. Some light passes into the air above, and the part that reflects back into the water makes an angle to the normal of:
10 degrees
What color does the moon often appear, during a total lunar eclipse?
Red/orange
If you want to use a converging lens of 4 cm focal length as a magnifying glass to look at the fine details on a coin, you should put the coin where?
3.9 cm from the lens, to obtain a virtual enlarged image
A lens with a power of +7 diopters has a focal length of
(1/7)th meter
For myopia, the eye doctor prescribes:
Diverging lens
Hypermetropia (hyperopia) is also know as
Far-sightedness
If you try to read a book, but the image forms behind your retina (outside your eyeball), then you need converging glasses (positive power) and your problem is called:
Hypermetropia (hyperopia)--far-sightedness
A butterfly at eye level is 30 cm in front of a plane mirror. You are behind the butterfly, 50 cm from the mirror. What is the distance between your eye and the butterfly's image in the mirror?
80 cm
My movie projector has a lens with 200 mm focal length. When projecting "E.T." in a large room, each film frame should pass about how far from the center of the lens?
202mm
When you look through a diverging lens, you always see a
Virtual image, right-side up
In which substance does light move the slowest?
Diamond
If a red light signal and a radio signal were emitted simultaneously from a distant star system, which would reach our solar system first?
Both would reach us at the same time
A lens with a positive power (for example +2 diopters) must be a:
Converging lens (one that brings parallel rays of light together to a focus)
Which one of these parts of the electromagnetic spectrum has the highest frequency?
Gamma rays
The shadow that is totally dark and tapers down to a point is called the:
Umbra
If a fish looks upward at 45 degrees with respect to the normal of the water's surface, it sees:
Clouds in the sky
If you are standing 6 feet away from a flat mirror, what is the distance between you and your image in the mirror?
12 feet
The people that see a partial solar eclipse are the people that observe from the:
Penumbra
It is difficult to see the road ahead of your car on a rainy night because wet roads have:
More mirror-like reflection, which bounces your headlight beam away from you