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Wavelength of an x-ray?


Ultraviolet (uv) wavelength

100A--4000 A

Visible light wavelength


What is below visible light


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:



Speed of light--300,000 Km/s

Speed of light slows down the most in what substance?


Speed of light slows down to .75 in:


1A =

The size of an atom

Speed of light slows down the least in:


What slows light down the most?


Why does light slow down in substances?

Absorption and re-emission

Glass blocks most of what kind of light?

Ultraviolet and infrared


Shadow; complete darkness; can't see the light source


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


The white crown glow in the outer atmosphere


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?


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:



A bending of light caused by change of speed as light passes from one medium to another.


Perpendicular to surface

Refraction and bending cause a:

Slowing down of light. And vice versa.


Separation into colors

What color of light slows down the most?

(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?


In the secondary rainbow what color is closest to the anti-sun?


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)?


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:


Refraction, Bending

Light Slows down!

Which color slows more than red?


Which color bends more than red?



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


Light travels slower in ________ air


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:


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


Diopters of a "strained" eye....for reading fine print


+60 = power =1/f

f = 1/60m


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


Loss of sight with aging

Diopters in average adult?


Diopters in grandparents eye?


Cure for Presbyopia (old)?

Bi-focals! Glasses with +0 on top and +3 on bottom

What color of visible light has the lowest frequency?


Which color of visible light has the highest frequency?


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.


Partially Blocked


Completely blocked

Do Earth and Moon always cast shadows?



Located on edge of eye
see black and white
Detect motion
Used in dark


Located in fovea (center)
see color
Detect fine print
Need bright lights

What has the longest wavelength?


Which has the shortest wavelength? UV or IR?


Which has a higher frequency? UV or IR?


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
Ultraviolet rays

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:


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)

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