PHYS 102 CHAPTER 8 AND 9 HOMEWORK
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The generator at a power plant produces AC at 22,000 V. A transformer steps this up to 295,000 V for transmission over power lines. If there are 2,200 turns of wire in the input coil of the transformer, how many turns must there be in the output coil? What is the wavelength of the 46,000Hz radio wave used by "radiocontrolled" clocks and wristwatches? A piece of iron is heated with a torch to a temperature of 558 K. How much more energy does it emit as blackbody radiation at 558 K than it does at room temperature, 295 K? What is the wavelength of the peak of the blackbody radiation curve for the human body (T = 311 K)? (Enter your answer to at least two decimal places.) The blackbody radiation emitted from a furnace peaks at a wavelength of 6.2 106 m (0.0000062 m). What is the temperature inside the furnace? The wavelength of an electromagnetic wave is measured to be 5.40 107 m. A small object is placed to the left of a convex lens and on its optical axis. The object is 30 cm from the lens, which has a focal length of 19 cm. If the object is moved to a position 28 cm to the left of the lens, what will the image position be? (A positive value for p, or position, means the image is on the right side of the lens.) A camera is equipped with a lens with a focal length of 31 cm. When an object 1.1 m (110 cm) away is being photographed, what is the magnification? List the main types of electromagnetic waves in order of increasing frequency. Give at least one useful application for each type of wave. Aircraft equipped with powerful radar units are forbidden from turning them on when on the ground near people. Explain why this is so.
Which type of EM wave does your body emit most strongly? Stars emit radiation whose spectrum is very similar to that of a blackbody. Imagine two stars identical in size, each of which is at the same distance from us. One of the stars appears reddish in color, while the other one looks distinctly bluish. Based on this information, what can you say about the relative temperatures of the two stars? Which is the hotter? How do you know? Describe the greenhouse effect that is occurring in the Earth's atmosphere. How does the ionosphere affect the range of radio communications?