Sections
Chapter Review

Chapter Review

Concept Items

15.1The Electromagnetic Spectrum

1.

Use the concepts on which Maxwell’s equations are based to explain why a compass needle is deflected when the compass is brought near a wire that is carrying an electric current.

1. The charges in the compass needle and the charges in the electric current have interacting electric fields, causing the needle to deflect.
2. The electric field from the moving charges in the current interacts with the magnetic field of the compass needle, causing the needle to deflect.
3. The magnetic field from the moving charges in the current interacts with the electric field of the compass needle, causing the needle to deflect.
4. The moving charges in the current produce a magnetic field that interacts with the compass needle’s magnetic field, causing the needle to deflect.
2.

Consider these colors of light: yellow, blue, and red. Part A. Put these light waves in order according to wavelength, from shortest wavelength to longest wavelength. Part B. Put these light waves in order according to frequency, from lowest frequency to highest frequency.

1. wavelength: blue, yellow, red

frequency: blue, yellow, red
2. wavelength: red, yellow, blue

frequency: red, yellow, blue
3. wavelength: red, yellow, blue

frequency: blue, yellow, red
4. wavelength: blue, yellow, red

frequency: red, yellow, blue
3.

Describe the location of gamma rays on the electromagnetic spectrum.

1. At the high-frequency and long-wavelength end of the spectrum
2. At the high-frequency and short-wavelength end of the spectrum
3. At the low-frequency and long-wavelength end of the spectrum
4. At the low-frequency and short-wavelength end of the spectrum
4.

In which region of the electromagnetic spectrum would you find radiation that is invisible to the human eye and has low energy?

1. Long-wavelength and high-frequency region
2. Long-wavelength and low-frequency region
3. Short-wavelength and high-frequency region
4. Short-wavelength and low-frequency region

5.

Light travels at different speeds in different media. Put these media in order, from the slowest light speed to the fastest light speed: air, diamond, vacuum, water.

1. diamond, water, air, vacuum
2. vacuum, diamond, air, water
3. diamond, air, water, vacuum
4. air, diamond, water, vacuum
6.
Visible light has wavelengths in the range of about . What does this indicate about the approximate thickness of the wall of a soap bubble? Explain your answer.
1. The thickness of the bubble wall is ten times that of the wavelength of light.
2. The thickness of the bubble wall is similar to that of the wavelength of light.
3. The thickness of the bubble wall is half the wavelength of light.
4. The thickness of the bubble wall equals the cube of the wavelength of light.
7.

Bright sunlight is reflected from an icy pond. You look at the glare of the reflected light through polarized glasses. When you take the glasses off, rotate them 90°, and look through one of the lenses again, the light you see becomes brighter. Explain why the light you see changes.

1. The glass blocks horizontally polarized light, and the light reflected from the icy pond is, in part, polarized horizontally.
2. The glass blocks vertically polarized light, and the light reflected from the icy pond is, in part, polarized vertically.
3. The glass allows horizontally polarized light to pass, and the light reflected from the icy pond is, in part, polarized vertically.
4. The glass allows horizontally polarized light to pass, and the light reflected from the icy pond is, in part, polarized horizontally.

8.

Explain how thin-film interference occurs. Discuss in terms of the meaning of interference and the pathways of light waves.

1. For a particular thickness of film, light of a given wavelength that reflects from the outer and inner film surfaces is completely in phase, and so undergoes constructive interference.
2. For a particular thickness of film, light of a given wavelength that reflects from the outer and inner surfaces is completely in phase, and so undergoes destructive interference.
3. For a particular thickness of film, light of a given wavelength that reflects from the outer and inner film surfaces is completely out of phase, and so undergoes constructive interference.
4. For a particular thickness of film, light of a given wavelength that reflects from the outer and inner film surfaces is completely out of phase, and so undergoes no interference.
9.

When you move a rope up and down, waves are created. If the waves pass through a slot, they will be affected differently, depending on the orientation of the slot. Using the rope waves and the slot as a model, explain how polarizing glasses affect light waves.

1. If the wave—electric field—is vertical and slit—polarizing molecules in the glass—is horizontal, the wave will pass.
2. If the wave—electric field— is vertical and slit—polarizing molecules in the glass—is vertical, the wave will not pass.
3. If the wave—electric field—is horizontal and slit—polarizing molecules in the glass—is horizontal, the wave will pass.
4. If the wave—electric field—is horizontal and slit—polarizing molecules in the glass—is horizontal, the wave will not pass.

10.

Visible light has a range of wavelengths from about 400 nm to 800 nm . What is the range of frequencies for visible light?

1. 3.75 × 106 Hz to 7.50 × 106 Hz
2. 3.75 Hz to 7.50 Hz
3. 3.75 × 10−7 Hz to 7.50 × 10−7 Hz
4. 3.75 × 1014 Hz to 7.50 × 1014 Hz
11.

Light travels through the wall of a soap bubble that is 600 nm thick and is reflected from the inner surface back into the air. Assume the bubble wall is mostly water and that light travels in water at 75 percent of the speed of light in vacuum. How many seconds behind will the light reflected from the inner surface arrive compared to the light that was reflected from the outer surface?

1. 4.0 × 10–8 s
2. 5.3 × 10–6 s
3. 2.65 × 10–15 s
4. 5.3 × 10–15 s

Critical Thinking Items

15.1The Electromagnetic Spectrum

12.

Standing in front of a fire, we can sense both its heat and its light. How are the light and heat radiated by the fire the same, and how are they different?

1. Both travel as waves, but only light waves are a form of electromagnetic radiation.
2. Heat and light are both forms of electromagnetic radiation, but light waves have higher frequencies.
3. Heat and light are both forms of electromagnetic radiation, but heat waves have higher frequencies.
4. Heat and light are both forms of electromagnetic radiation, but light waves have higher wavelengths.
13.

Light shines on a picture of the subtractive color wheel. The light is a mixture of red, blue, and green light.

Part A—Which part of the color wheel will look blue? Explain in terms of absorbed and reflected light.

Part B—Which part of the color wheel will look yellow? Explain in terms of absorbed and reflected light.
1. The yellow section of the wheel will look blue because it will reflect blue light and absorb red and green.
2. The blue section of the wheel will look yellow because it will reflect red and green light and absorb blue.
1. The blue section of the wheel will look blue because it will absorb blue light and reflect red and green.
2. The yellow section of the wheel will look yellow because it will absorb red and green light and reflect blue.
1. The yellow section of the wheel will look blue because it will absorb blue light and reflect red and green.
2. The blue section of the wheel will look yellow because it will absorb red and green light and reflect blue.
1. The blue section of the wheel will look blue because it will reflect blue light and absorb red and green.
2. The yellow section of the wheel will look yellow because it will reflect red and green light and absorb blue.
14.

Part A. When you stand in front of an open fire, you can sense light waves with your eyes. You sense another type of electromagnetic radiation as heat. What is this other type of radiation?

Part B. How is this other type of radiation different front light waves?
1. X-rays
2. The X-rays have higher frequencies and shorter wavelengths than the light waves.
1. X-rays
2. The X-rays have lower frequencies and longer wavelengths than the light waves.
1. infrared rays
2. The infrared rays have higher frequencies and shorter wavelengths than the light waves.
1. infrared rays
2. The infrared rays have lower frequencies and longer wavelengths than the light waves.
15.

Overexposure to this range of EM radiation is dangerous, and yet it is used by doctors to diagnose medical problems.

Part A—Identify the type of radiation.

Part B—Locate the position of this radiation on the EM spectrum by comparing its frequency and wavelength to visible light.

Part C—Explain why this radiation is both dangerous and therapeutic in terms of its energy, based on your answer to Part B.
1. A. X-rays

B. X-rays have shorter wavelengths $(1×10–8–5×10–12 m)(1×10–8–5×10–12 m)$ and higher frequencies than visible light

C. X-rays have low energies because of their high frequencies, and so can penetrate matter to greater depths.
2. A. X-rays

B. X-rays have shorter wavelengths $(1×10–8–5×10–12 m)(1×10–8–5×10–12 m)$ and higher frequencies than visible light

C. X-rays have low energies because of their low frequencies, and so can penetrate matter to greater depths.
3. A. X-rays B. X-rays have longer wavelengths $(1×10–6–5×10–7 m)(1×10–6–5×10–7 m)$ and higher frequencies visible light

C. X-rays have high energies because of their high frequencies, and therefore can penetrate matter to greater depths.
4. A. X-rays

B. X-rays have shorter wavelengths $(1×10–8–5×10–12 m)(1×10–8–5×10–12 m)$ and higher frequencies than visible light

C. X-rays have high energies because of their high frequencies, and so can penetrate matter to greater depths.

Problems

16.

Design an experiment to observe the phenomenon of thin-film interference. Observe colors of visible light, and relate each color to its corresponding wavelength. Comparison with the magnitudes of visible light wavelength will give an appreciation of just how very thin a thin film is. Thin-film interference has a number of practical applications, such as anti-reflection coatings and optical filters. Thin films used in filters can be designed to reflect or transmit specific wavelengths of light. This is done by depositing a film one molecular layer at a time from a vapor, thus allowing the thickness of the film to be exactly controlled.

Safety Warning
• EYE SAFETY—Chemicals in this lab are poisonous if ingested. If chemicals are ingested, inform your teacher immediately.
• FUMES—Certain chemicals or chemical reactions in this lab create a vapor that is harmful if inhaled. Follow your teacher's instructions for the use of fume hoods and other safety apparatus designed to prevent fume inhalation. Never smell or otherwise breath in any chemicals or vapors in the lab.
• FLAMMABLE—Chemicals in this lab are highly flammable and can ignite, especially if exposed to a spark or open flame. Follow your teacher's instructions carefully on how to handle flammable chemicals. Do not expose any chemical to a flame or other heat source unless specifically instructed by your teacher.
• HAND WASHING—Some materials may be hazardous if in extended contact with the skin. Be sure to wash your hands with soap after handling and disposing of these materials during the lab.
• WASTE—Some things in this lab are hazardous and need to be disposed of properly. Follow your teacher's instructions for disposal of all items.
Materials
• A large flat tray with raised sides, such as a baking tray
• Small volumes of motor oil, lighter fluid or a penetrating oil of the type used to loosen rusty bolts, and cooking oil
• Water
• A camera
1. Thin-film interference causes colors to appear on the surface of a thin transparent layer. Do you expect to see a pattern to the colors?
2. How could you make a permanent record of your observations?
3. What data would you need to look up to help explain any patterns that you see?
4. What could explain colors failing to appear under some conditions?