Module 15 Quiz

Question 1

A transverse wave composed of an oscillating electric field and a magnetic field that oscillates perpendicular to the electric field

Answer 1

Electromagnetic wave

Question 2

The angle of reflection equals the angle of incidence.

Answer 2

The Law of Reflection

Question 3

Explain the wave theory of light, the particle theory of light, and the quantum-mechanical theory of light.

Answer 3

“The wave theory of light views light as two transverse waves, one made of an oscillating magnetic field and the other an oscillating electric field. The particle theory of light views a ray of light as a beam of individual particles called photons. The quantum-mechanical theory says that light is both a particle and a wave. It is made up of individual packets that behave like particles, but the packet is actually made up of a wave”.

Question 4

Sound waves cause air to oscillate. What do light waves oscillate?

Answer 4

“Light waves oscillate a magnetic field and an electric field”. Each one oscillates perpendicular to the other, as well as perpendicular to the direction of travel.

Question 5

What does Einstein’s Special Theory of Relativity say about the speed of light?

Answer 5

Einstein’s Special Theory of Relativity says that “nothing with mass can travel faster than the speed of light”.

Question 6

Light is traveling through water and suddenly breaks the surface and travels through air. Did light’s speed increase, decrease, or stay the same once it left the water?

Answer 6

Unlike sound, light travels slower in liquids than gases. Thus, the “light’s speed increased once it left the water”.

Question 7

Order the following colors in terms of increasing wavelength: orange, violet, yellow, green. In other words, list the color corresponding to the smallest wavelength first, and end with the color that corresponds to the longest wavelength.

Answer 7

The acronym ROY G. BIV allows us to remember the relative size of the colors’ wavelengths. Red is longest and violet is shortest. Thus, in terms of increasing wavelength, the colors are: “violet, green, yellow, and orange”.

Question 8

Order the colors in problem #6 in terms of increasing frequency. Once again, start with the lowest frequency and end with the highest frequency.

Answer 8

Wavelength and frequency are inversely proportional. Thus, in terms of increasing frequency, it is the reverse of the previous order: “orange, yellow, green, and violet”.

Question 9

Do radio waves have higher or lower frequencies than visible light? What about X-rays?

Answer 9

Radio waves have wavelengths longer than visible light while X-rays have shorter wavelengths. This comes from Figure 15.3. Just like the visible light colors, you need not memorize any values for the wavelengths, but of the major categories in the figure, you need to know their relative wavelengths. Since frequency and wavelength are inversely proportional, “radio waves have lower frequencies than visible light, while X-rays have higher frequencies”.

Question 10

Infrared light is given off by any object that is losing heat. The human body is almost always losing heat to the environment. Why, then, don’t human bodies glow at night, since they are emitting light?

Answer 10

“Infrared light is not visible”. Thus, even though human bodies constantly emit infrared light, we cannot see that happening. There are special devices you can get that do, indeed, detect the infrared light that the human body emits. This allows you to see living organisms and other hot objects, even in the darkest of nights.

Question 11

Light hits a mirror, making an angle of 15 degrees relative to a line drawn perpendicular to the mirror’s surface. What angle does the reflected light make with the same line?

Answer 11

By the Law of Reflection, “the reflected light also makes a 15 degree angle relative to that line”.

Question 12

In the following diagram, will the man see his foot, despite the fact that the mirror does not reach the ground?

Answer 12

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Question 13

When light travels from one substance to another, what two things can happen to the direction of the light ray’s travel?

Answer 13

“The light ray can be reflected or refracted”.

Question 14

In a physics experiment, a light ray is examined as it travels from air into glass. If the angle that the light ray makes with a line perpendicular to the glass surface is measured, will the refracted ray bend toward or away from that line?

Answer 14

When light travels from a substance in which it moves quickly to a substance in which it moves slowly, the light bends towards the perpendicular. Since light moves faster in air than in glass, “the light will bend towards the perpendicular line”.

Question 15

When you look at objects underwater from above the water, they appear to be at a different position than their actual position. Why?

Answer 15

In order for you to see the objects underwater, light must travel from the object to your eyes. Thus, the light must travel out of the water and into the air. “When light travels from water to air, it bends. This causes your mind to form a false image of the object in a slightly different location”.

Question 16

In order for you to see a rainbow, what three conditions must be met?

Answer 16

“There must be water droplets suspended in the air, the sun must be shining on them from behind you, and the sun must be at a certain angle (or height in the sky)”. The water droplets cause the refraction. In order to separate the colors enough to see them, however, the light must be refracted, reflected, and refracted again (see Figure 15.6). To do that, light must enter the water droplet on the side from which you are viewing it.

Question 17

What is the difference between a converging lens and a diverging lens?

Answer 17

“A converging lens causes light rays to bend so that they converge to a single point. Diverging lenses cause light rays to bend away from each other”.

Question 18

Which of the following lenses is a converging lens? Which is a diverging lens?

Answer 18

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Question 19

What is special about the way the eye focuses light as compared to the way a camera focuses light?

Answer 19

“The eye focuses light by changing the shape of its lens. A camera focuses light by moving the position of the lens”. The eye’s method is faster and much more precise.

Question 20

Suppose the cone cells on your retina that sense red light no longer work. If you look at a white piece of paper, what color would it appear to be? If you look at a red piece of paper, what color would it appear to be?

Answer 20

If your red cone cells no longer worked, your brain would think that you never saw red light. When the white light reflected off of the paper and hit your eyes, then, your green cone cells would send signals to your brain, as would your blue cone cells. As a result, the “white paper would appear to be blue-green or cyan”. If you looked at a red piece of paper, it is red because it only reflects red light. Thus, it would send only red light to your eyes. You cannot see red light, however, “so the red paper would appear to be black”. In actual fact, it would probably appear gray, because the other cells in your eyes (rods) detect the presence of light without detecting color. Thus, your brain would receive signals from the rods telling it that light was there, but there would be no cone cell signals to indicate the color. The brain would be a bit confused, but it would probably form a grayish image, as if you were seeing only in black and white.

Question 21

A shirt is dyed so that it looks violet. What colors of light does the dye absorb?

Answer 21

In order to look violet, it must absorb all colors except violet. “Thus, it absorbs red, yellow, orange, green, blue, and indigo light”.

Question 22

A cyan dye is made of a mixture of substances that absorb all light colors except blue and green. If you took a cyan piece of paper and placed it in a dark room and shined red light on it, what would you see? What would you see if you shined green light on it?

Answer 22

Since cyan absorbs all colors except blue and green, it will absorb any red light shone on it. As a result, no light will make it to your eyes. “In red light, then, the paper would look black”. When you shined green light on it, the green light would be reflected. There would be no blue to mix with it, though. “In green light, the paper would look green”.

Question 23

In the following diagram, will the man see his foot, despite the fact that the mirror does not reach the ground?

Answer 23

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