Chapter 6: Light: The Cosmic Messenger
 
Conceptual Quiz
 

1 .       Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use? [Hint]



2 .       Which of the following statements is true of green grass? [Hint]



3 .       Which of the following best describes why we say that light is an electromagnetic wave? [Hint]



4 .       Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz. Which of the following statements is true? [Hint]



5 .       Gamma rays have a very small ______. [Hint]



6 .       Which of the following statements about X-rays and radio waves is NOT true? [Hint]



7 .       Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength? [Hint]



8 .       Which of the following conditions will lead you to see an absorption line spectrum from a cloud of gas in interstellar space? [Hint]



9 .       The following diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. Which labeled transition represents an electron that absorbs a photon with 10.2 eV of energy? [Hint]



10 .       No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would NOT produce a close approximation to a thermal radiation spectrum? [Hint]



11 .       Which of the following statements about thermal radiation is ALWAYS true? [Hint]



12 .       The star Sirius has a surface temperature about twice that of the Sun (12,000 Kelvin for Sirius versus 6,000 Kelvin for the Sun). Per unit surface area, how much more energy does Sirius radiate than the Sun? [Hint]



13 .       The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible light spectrum of the Sun? [Hint]



14 .       All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays? [Hint]



15 .       Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color? [Hint]



16 .       If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet? [Hint]



17 .       Suppose that two stars are identical in every way --- for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth --- except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart? [Hint]



18 .       Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which one? [Hint]



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