Chapter 22 review


    Conceptual questions
      Section 22.1
      1. Describe the relationship between the index of refraction of a material and the speed light travels in that material.
      2. Sound waves cannot travel through a vacuum, but electromagnetic waves can. Can you think of an example of an electromagnetic wave traveling through a vacuum?
      3. When electromagnetic waves enter a new medium, such as water, what happens to their speed? Is this similar to what happens to sound waves?
      4. What happens when you slightly change the frequency of light in the visible spectrum? How does this compare to changing the frequency of a sound wave?
      5. Easy Which color of visible light has the lowest frequency? Which color has the highest frequency?
      6. Easy Why was the equation c =  used in this chapter instead of v = ?
      7. Medium What is the range of wavelengths (in nanometers) that the human eye can see?
      8. Medium How are frequency and wavelength related for light?
      9. Challenging In general, the speed of light decreases in denser materials whereas the speed of sound increases. For example, light travels at 3×108 m/s in air, 2.26×108 m/s in water, and 1.24×108 m/s in diamond. Sound travels travels at 343 m/s in air, 1,483 m/s in water, and 12,000 m/s in diamond. Why do you think this is? What is different about the way light and sound propagate?
      Section 22.2
      1. The index of refraction of glass is larger for blue light than for green light. Which kind of light, blue or green, travels faster through glass?
      2. The index of refraction of glass is larger for blue light than for green light. Which kind of light, blue or green, will have its path bent more when dispersed through a triangular glass prism?
      3. Cell phones expose users to radio frequency (RF) radiation. Possible health effects of this exposure are the subject of current study and controversy. Research this issue by citing and quoting from two studies or articles: one providing evidence of a medical risk and the other indicating that any risk is negligible.
      4. What characteristic of x-rays allows them to be used to image the bone structure of patients in medical facilities?
      1. How do doctors use gamma rays to help treat their patients?
      2. Inspect a chart of the electromagnetic spectrum and identify what type of electromagnetic radiation corresponds to each of the following.
        1. wavelength of 10 μm
        2. frequency of 1,050 kHz
        3. wavelength of 656 nm
        4. frequency of 0.1 THz
      3. Easy While skiing, Daniela looked at her friend Mauro through a thin piece of plastic but found it difficult to see him because of the glare off the snow. Why was the glare from the snow reduced when she rotated the plastic by 90°?
      4. Medium How does a microwave oven cook food? Research how this technology works and write a short essay describing how the microwaves are generated, what wavelengths or frequencies are involved, how the waves heat the food, and how the machine prevents the microwaves from escaping.
      5. Medium The Boston Globe reported in 2012 that a private company was taking pictures of area houses using cars with specially designed, roof-mounted cameras. “The cameras were designed to take pictures of homes on either side of the car as we roamed the streets of Belmont—pictures of heat seeping out from windows, eaves, and inadequately insulated walls... [This] was what you might call HeatView.”
        1. At what portion of the electromagnetic spectrum do you think the cameras operate? Why?
        2. If it is legal to take pictures of the houses from the street using ordinary cameras operating at visible-light wavelengths, do you think it would be legal to take pictures at the wavelengths that these heat-sensing cameras are operating? Explain.
        3. The Globe article concludes, “Some architects, homeowners, and commercial landlords are already hunting for ways to cut energy consumption. But the key to success for this crop of software start-ups—and the key to curbing our need for new generating capacity—will be getting the mainstream to care, and spend money.” Write a short essay describing how a company might use the information gathered by these heat-sensitive cameras to sell customers energy-saving upgrades to their homes. In your essay, communicate clearly what scientific information you have taken from the article and what inferences you made from the article.
      6. Medium Compare photons detected by a CAT scanning machine to those emitted by a sunning lamp. Which photons have longer wavelength? Higher frequency? Higher energy?

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