Chapter 22 review


    Quantitative problems
      Section 22.2
      1. Easy Compare 980 on the AM radio dial with 98 on the FM dial.
        1. Which frequency is higher?
        2. By what factor is it higher?
        3. What is the wavelength corresponding to each frequency?
        4. Which has a longer wavelength?
      2. Medium Television broadcasts on frequencies between 54 MHz (channel 2) and 806 MHz (channel 69).
        1. What are the wavelengths corresponding to these frequencies?
        2. How do these frequencies compare to AM/FM radio broadcast frequencies?
      3. Challenging Communication with submarines typically uses frequencies below 1 kHz.
        1. What wavelengths of electromagnetic radiation does that correspond to?
        2. Name an object in your everyday environment that is similar in size to those wavelengths.
        3. How can such wavelengths be broadcast?
        4. Can the submarines broadcast at these wavelengths?
      Section 22.3
      1. Calculate the energy of a 500 nm photon of light.
      2. Easy Approximately how many photons of infrared light (λ = 6 μm) are there in 1 eV of energy?
      3. Easy A typical radio wave has a wavelength of 6 cm.
        1. Approximately how many photons of this type of radio “wave” are there in 1 eV of energy?
        2. Why might electromagnetic radiation at radio wavelengths often be treated as waves, not particles?
      4. Easy Sort the following kinds of electromagnetic radiation in order of increasing energy: ultraviolet light, visible light, infrared light, radio waves, gamma rays, and x-rays.
      5. Medium One electron volt or eV is an energy of 1.602×10−19 J. The kiloelectron volt (keV) is often used to express the energy of photons in a particular region of the electromagnetic spectrum. Using an electromagnetic spectrum chart, determine what kind of electromagnetic radiation corresponds to an energy of 1 keV.
      1. Medium Chromium has a work function of 7.2×10−19 J. What is the threshold frequency for this material?
      2. Medium A metal only ejects electrons by the photoelectric effect when a light with a wavelength of 286 nm or smaller shines on the metal. What is the work function of the metal?
      3. Medium Some kinds of electromagnetic radiation are typically described using units of energy, such as the electron volt (eV, where 1 eV = 1.602×10−19 J).
        1. What frequency corresponds to electromagnetic radiation having an energy of 2.0 keV?
        2. What kind of electromagnetic radiation is it?
      4. Medium How many photons of orange light (λ = 600 nm) does it take to make 1 J of energy?
      5. Medium A student who was investigating the photoelectric effect measured the threshold frequency for sodium to be 4.4×1014 Hz. The student subsequently increased the frequency of the incident radiation to 7.0×1014 Hz.
        1. What kind of electromagnetic radiation corresponds to the frequencies of 4.4×1014 and 7.0×1014 Hz?
        2. Based on his measurement, how much work is required to free an electron from the surface of the metal sodium?
        3. How much kinetic energy did the electrons ejected from the surface have when the frequency of the incident light was 4.4×1014 Hz?
        4. How much kinetic energy did the electrons ejected from the surface have when the frequency of the incident light was 7.0×1014 Hz?
      6. Challenging A student investigates the photoelectric effect using calcium. For each frequency of the incident light, she measures the stopping voltage that she needs to apply between the electrodes to stop the flow of electrons. Graph the data and use your graph to find the threshold frequency for calcium.

        Frequency f of
        incident light
        (Hz)
        Stopping voltage V
        (V)
        0.75×10150.1
        0.80×10150.3
        0.95×10150.7
        1.20×10151.3

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