Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 4: Light and Atoms

Problems

1
Use the Sun's distance of 150 million kilometers to calculate how long light takes to travel from the Sun to the Earth.
2
Suppose you are operating a remote-controlled spacecraft on Mars from a station here on Earth. How long will it take the craft to respond to your command if Mars is at its nearest point to Earth? Use data in the appendix for your calculations.
3
A frequency commonly used for cell phones, wireless internet, and even in microwave ovens is 2.4 GHz. What is the wavelength of this radiation?
4
A solar flare emits X rays and radio waves simultaneously. Which reaches the Earth first? If the X rays have a wavelength of 0.25 nanometers and the radio waves have a wavelength of 6 cm, how many times larger is the frequency of the X rays than the radio waves?
5
Your body temperature is about 300 K. At what wavelength do you radiate most strongly? What region of the electromagnetic spectrum is this? Do you understand now how a rattlesnake can bite you in the dark?
6
An electric stove burner on "high" radiates most strongly at about 2000 nanometers. What is its temperature?
7
The Earth's temperature averaged over the year is about 300 Kelvin. At what wavelength does it radiate most strongly? In what part of the electromagnetic spectrum does this wavelength lie? Can you see it?
8
Sketch an atom emitting light. Does the electron end up in a higher or lower orbit? Repeat for an atom absorbing light.
9
Calculate the Doppler shift for blue light (wavelength of 500 nanometers) reflected off a sports car traveling away from you at 150 km/hr. What is Δλ? What is the wavelength you see? Could we see the shift in color with our eyes?
10
You are analyzing a radio spectrum of an outer part of a distant spiral galaxy. A spectral line expected to be at 21 centimeters is instead measured to be at 21.010 centimeters. Is the outer part of the galaxy rotating toward or away from you? How fast is that part of the galaxy moving?
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