Mastering Physics Homework#2

The sky is blue due mainly to atmospheric _________.

***scattering***

Ninety-five percent of light incident on a mirror is reflected. How much light is reflected when three of these mirrors are arranged so light reflects from one after the other?

**86%** 95% 81% 85% 90%

Why does the sky normally appear blue?

**Air molecules have resonances in the ultraviolet, so they scatter blue light more than red light.**

Why does the sky sometimes appear whitish?

**Large particles in the atmosphere scatter longer wavelength light that adds to the blue light to create white light.**

Part A:What happens when light from the Sun interacts with the molecules of the atmosphere?

**The molecules scatter the light.**

What do the electrons affected by illumination do when they are made to vibrate with greater energy?

**They reemit more light or collide with neighbors, thereby converting light energy to more internal energy. *

The blackness of the type on a page is due to _________.

**absorption** reflection interference scattering

A sunset appears red in color due to _________.

**higher frequencies of light scattered away**

Why does the color of sunsets vary from day to day?

Different particles in the air each day scatter and absorb different wavelengths of light, thus giving the sky many different colors.

What is Fermat's principle of least time?

Light takes the quickest path in going from one place to another.

Why does the Sun look reddish at sunrise and sunset but not at noon?

The longer path length of sunlight at sunrise and sunset scatters out more blue light.

The color of seawater is a result of the subtraction of what color?

Violet Yellow **Red** Green

What accounts for the whiteness of a cloud?

Water droplets of different sizes scatter a variety of light frequencies, resulting in a white cloud.

What fraction of the light shining straight at a piece of clear glass is reflected from the first surface?

About 10% None About 90% **About 4%**

How does incident light that falls on an object affect the motion of electrons in the atoms of the object?

Incident light makes the electrons oscillate. The electrons then emit light or absorb the light and convert it to heat.

Part E: Why is the sunset red?

Only the low-frequency red light penetrates the thick layers of atmosphere when the Sun is low in the sky.

Relative to the distance of an object in front of a plane mirror, how far behind the mirror is the image?

The image is the same distance behind the plane mirror as the object is in front of it.

Part C: What kinds of molecules will scatter the low frequencies of light?

**large molecules**

Part B: What kinds of molecules scatter high frequencies of light?

**small molecules**

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

**time** energetic path dense material distance

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

**twice your speed.** your speed. half your speed. none of the above

You photograph the image of your little sister, who stands 2 meters in front of a plane mirror. Holding the camera beside her head, the distance to her image is

3 meters. 1 meter. 2 meters. **4 meters.** none of the above

What is the effect on the color of a cloud when it contains an abundance of large droplets?

The cloud becomes bright. **The cloud becomes dark.** The cloud becomes transparent. The cloud becomes reddish.

What color results when red is subtracted from white light?

Magenta **Cyan** Yellow Ultraviolet

What part of the electromagnetic spectrum is most absorbed by water?

Red Blue Green **Infrared**

Part D:Why is the sky blue when the Sun is overhead?

The molecules in the atmosphere scatter blue light more than any other light, so the sky looks blue.

Clouds are white due to _________.

refraction interference **scattering** absorption