PY 131 Chapter 28 Conceptual Academy

When you look in a mirror, you are seeing yourself

from behind.

What does a mirror do to the up-down axis?

Nothing.

In this lesson Blinky Bill illustrates reflection

of himself in a mirror.

This lesson concludes with a photo of

Stephanie Hewitt dipping a glass rod into a fluid.

Light bends into a transparent medium because

of interactions with that medium.

The only physicist illustrated in this lesson is

Isaac Newton.

A fish looking up to a calm surface sees a distorted

180 degree view above water.

From the edge of a pond you see a fish. This fish is actually

Farther from you than it looks to be

This lesson emphasizes pinhole images of

both of these

Through glass, blue light refracts more than red light because it travels

slower.

The blackness of the type on this page is due to

absorption.

Light travels a path from one location to another in the least

time.

Specular reflection is common in the light reflected from

a mirror.

A mirage is the result of atmospheric

refraction.

Which of the following changes when light is refracted?

Speed.

Dispersion of light from drops making up a rainbow have undergone refraction and internal

reflection.

A secondary rainbow in the sky is the result of a

a double reflection in drops.

Total internal reflection occurs when the speed of light in a material is

less than the speed outside the material.

A feature of a pinhole camera is that the image

is inverted.

A magnifying glass widens the angle through which

an object is viewed.

When white light travels from air into water, the color that refracts the most is

violet.

The redness of the Moon during a lunar eclipse results from

refraction by the Earth's atmosphere of Earth's sunrises and sunsets.

Rainbows exist because of light

both of these

Is the critical angle the least in glass, water, diamond, or a vacuum?

diamond

To see his full height, a boy that is 1 meter tall needs a mirror that is at least

0.50 m tall.

Mirages occus for road surfaces that are

warm.

What does Fermat's principle of least time apply to?

Both of these

(**Fermat's principle of least time applies to reflection.**

**Fermat's principle of least time applies to refraction.)**

What path will light take from one point to another?

The path of least time.

To compensate for refraction when spearing a fish it is best to throw your spear

below the sighted fish.

You wish to photograph the image of your little sister, who is standing 2 meters from a plane mirror. Holding the camera beside her head, you should set the distance for

4 meters.

How does light travel in optical fibers of uniform density?

Light travels in straight-line segments.

At night an underwater scuba diver aims his flashlight beam toward the surface at an angle of 15 degrees with the normal. Upon emerging, the beam angle will be

more than 15 degrees.

Why are rainbows not usually seen as complete circles?

Because the ground is usually in the way.

When a rainbow seen from an airplane sometimes forms a complete circle, the plane's shadow is

in the center of the rainbow.

To send a laser beam to a space station that is near the horizon and above the atmosphere, aim your laser

along your line of sight.

If the speed of light in a medium is two-thirds its speed in a vacuum, the medium's index of refraction is

0\.67.

Two plane mirrors are at right angles to each other. A coin placed near the mirrors has at most

3 images.

What is refraction of light a result of?

Differences in light's speed.

Refraction causes the bottom of a swimming pool to appear

closer to the surface than it actually is.

When does diffuse reflection occur?

When the size of surface irregularities is large compared to the wavelength of the light used.

A surface that is considered rough for infrared waves may be polished for

radio waves

How does a ray of light bend when it passes from water to air at a non 90 degree angle?

The light bends away from the normal.

As monochromatic light passes to and fro in glass and air, changes are observed in its

wavelength and speed.

What kind of lens can focus sunlight to make a flame?

Converging lens.

Which of these is the result of the different speeds of light in transparent materials?

**all of these**

**(mirages**

**rainbows**

**internal reflection**

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Primary rainbows are brighter than secondary rainbows because

there is one less reflection inside the water drops.

The critical angle for a transparent material is the angle at and beyond which all light within the material is

reflected.

Is your vision sharper when your pupil is dilated or constricted?

Constricted.

Is your image in a plane mirror virtual or real?

Virtual.

Object and image for a plane mirror lie

equal distances from the mirror.

Where does the image of the "infinitely-far-away" sun appear relative to the focal point?

At the focal point.

When does moonlight appear as a vertical column in the water?

When the water is slightly rough.

If you walk towards a mirror at a certain speed, the relative speed between you and your image is

twice your speed.

Magnification by a lens would be greater if light

traveled slower in glass than it does.

Objects that are infinitely far away are focused by a converging lens

at the focal point.

What kind of atmospheric filter effect creates a mirage?

Refraction.

Fermat's principle of least time could also be the principle of least distance for the case of

reflection.

When a fish looks upward at 45 degrees to the water's surface, it sees

the sky and possibly some hills.

What color does a raindrop disperse?

All the colors of the rainbow.

When a light beam emerges from water into air, the average light speed What happens to the speed of a light beam when it goes from water to air?

The speed increases.

A yellow-white candle flame reflected from a piece of red glass shows two images; one from each surface.

One image is yellow-white and the other red.

Will parallel rays of red and blue light passing through a convex lens produce images at the same location?

No. Blue light images closer to the lens.

Why is the secondary rainbow dimmer than the primary rainbow?

Because of an extra reflection and refraction in the drops.

When you view a distant rainbow, each single water drop contributes to the bow

a single color.

Do you see more or less of yourself when you hold a small mirror farther away at arm's length?

The same amount of yourself.

When light undergoes refraction, there is a change in its

wavelength.

Does atmospheric refraction make the day longer or shorter?

Atmospheric refraction makes the day longer.

What percent of light does a common window pane reflect?

4 percent.

As a light ray enters or exits a water-air interface at an angle of 15 degrees with the normal, it

always bends toward the normal.

What is the angle of emergance when light passes through an ordinary window pane?

The same as its angle of incidence.

Why does light refract when traveling from air into gas?

Because light travels slower in glass than in air.

Standing at the shore of a still lake, the reflected view of scenery on the far side of the lake is the view you would see if you were upside down with your eye in the line of sight

directly beneath you, as far below water level as you are above.

Newton's rings nicely illustrate

interference.

Ninety percent of light incident on a pane of glass passes through it. How much light will pass through two pieces of this glass?

81 percent

A hypothetical fish above the surface of water will see better if it has goggles that are

filled with water.

Are optical fibers used by surgeons, mechanics, or engineers?

(All of these.

surgeons. mechanics. engineers.

What type of lens spreads parallel light?

Diverging lens.

The elliptical shape of the Sun at sunset can be adequately explained by

both of these

When is light emitted?

When electron clouds of atoms are forced into oscillation.

Atmospheric refraction produces

longer daytimes.

In a vacuum, all the different colors of light travel at

the same speed.

What percentage of light is reflected off three consecutive incident mirrors?

86 percent

Does a beam of light travel fastest through glass, water, plastic, or air?

Air.

The twinkling of stars as seen from Earth is due to atmospheric

refraction

Where does light travel the fastest?

In a vacuum.

When you stand waist-deep in a swimming pool your legs appears shorter due to light

refraction.

Is chromatic aberration absent in converging lenses, diverging lenses, front surface plane mirrors, or plane mirrors?

Chromatic aberration is absent in front surface plane mirrors.

What is the shortest plane mirror you can use to see your entire image?

Half your height.

Strictly speaking, when a pulse of white light is incident on a pane of glass the first color to emerge is

red.

A person who sees more clearly under water with bare eyes is

nearsighted.

In "spearing" a blue fish with a red laser beam, you should aim your laser

below the sighted fish.

What causes chromatic aberration?

Different colors in a lens having different speeds.

What characteristics of light change when it reflects off a surface?

None of these.

The incident light ray, the reflected light ray, and the normal between them

lie in the same plane.

Is the image in a pinhole camera inverted or right-side up?

Always inverted.

A diver shines light up to 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.

Does the image in a pinhole camera become brighter or more clear when the hole is made larger?

The image becomes brighter.

In "spearing" a red fish with a red laser beam, you should aim your laser

directly at the sighted fish.

Mirages occurs for surfaces that are

**(both of these)**

**horizontal.**

**vertical.**

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What is the inversion of your image in a plane mirror an inversion of?

Front-back.