Chapter 22 review


    Conceptual questions
      Section 22.2
      1. When constructing the enclosure to detect infrared light in Investigation 22B on page 1277, why is it helpful to cover the inside of the box with black paper?
      2. Many sound waves can diffract around buildings—which means that a sound made on one side of the building can be heard on the other side. Light in the visible part of the spectrum, however, cannot diffract around a building—you can’t see what is on the other side of a building. What is the main difference between them? Does this suggest a part of the electromagnetic spectrum that would be able to diffract around a building?
      3. Medium When using a triangular glass prism to disperse white light, is it more effective to use a diffuse light source or a narrow beam of light?
      4. Challenging Why do night goggles detect infrared radiation? Why not gamma or ultraviolet radiation?
      Section 22.3
      1. Why shouldn’t you look directly at the Sun when using a hand-held visual spectroscope outdoors during a field investigation?
      2. Describe the photoelectric effect and how it relates to the dual nature of light.
      3. Polarized glasses block some of the light and reduce glare. Why is it still dangerous to look at the Sun when wearing polarized glasses?
      4. Easy How is the vibrational frequency of an electromagnetic wave related to its energy?
      5. Easy Explain what is meant by the number of “megapixels” in a digital camera.
      6. Easy For the signal of an AM radio station at 1,050 kHz, what does the frequency 1,050 kHz represent? Is it the frequency of the musical sounds broadcast by the station?
      7. Medium One student proposed a scientific explanation that light is a particle, based on the photoelectric effect. A second student tested the first student’s hypothesis by conducting the double slit experiment, which showed that light interferes as a wave. The second student therefore proposed the scientific explanation that light is a wave. In your evaluation of the two scientific explanations and the evidence, who is right?
      8. Medium In the double slit experiment for light, how will the spacing of the interference bands (or fringes) vary with the wavelength of the light?
      1. Challenging Sometimes a picture taken with a CCD-based camera shows a long streak trailing from a very bright source, such as a lamp, bright star, or the Sun. What property of the CCD do you think causes this?
      Quantitative problems
        Section 22.1
        1. How much faster do radio waves travel in a vacuum than infrared light?
        2. How many times faster is light than sound?
        3. Light takes approximately 8.3 min to travel from the Sun to the Earth. About how far is the Sun from Earth in kilometers?
        4. Astronomers often state the distances to other stars in terms of light-years. Using scientific notation, calculate the number of kilometers in one light-year. State your answer with two significant figures, using c = 3.0×108 m/s for the speed of light in a vacuum.
        5. You are directing a science-fiction movie in which Earthlings use light to communicate with the inhabitants of another planetary system. An Earth scientist sends a greeting and receives an answer a few seconds later. Is this possible given what you know about the speed of light? (The nearest star system to our own is roughly 4×1016 m away in the far-southern constellation of Centaurus.)
        6. Easy The Voyager 1 spacecraft is currently more than 19 billion km from the Earth. How long will it take a signal sent by the spacecraft to reach the Earth?
        Section 22.2
        1. Sort the following kinds of electromagnetic radiation in order of increasing wavelength: yellow light, microwaves, x-rays, ultraviolet light, and violet light.
        2. Sort the following kinds of electromagnetic radiation in order of increasing frequency: red light, radio waves, gamma rays, infrared light, and green light.
        3. An electromagnetic wave with the same frequency as the A string on a violin (440 Hz) would lie in what part of the electromagnetic spectrum? How about one with the same wavelength (78.4 cm)? Why are these different?
        4. Easy Calculate the frequency of electromagnetic radiation that has a wavelength of 5 μm. What kind of electromagnetic radiation is it?
        5. Easy The Very Large Array radio telescope often observes at a wavelength of 3.6 cm. What is the frequency of these radio waves in gigahertz (GHz)?

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