Astronomy Final Chapter 5

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

1 meter (Remember that, for a wave, wavelength frequency = speed. The speed of light is 300 million m/s.)

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

6,000 joules (1 watt = 1 joule/s, so a 100-watt light bulb uses 100 joules of energy per second. In 1 minute, it uses 60 100 = 6,000 joules of energy.)

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

The cloud is cool and lies between you and a hot star.

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

Star X is moving away from us faster than Star Y.

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?

The planet is rotating.

Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

The star is moving toward us.

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?

The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.

X rays have ________ frequency than radio waves.

higher

Gamma rays have a small ______.

wavelength