Any object warmer than absolute zero gives off some radiation, but its temperature determines how much energy it radiates, and in what forms. Here we study how changes in temperature affect the color and luminosity of stars, surfaces of planets, and other astonomical processes.

 1 What is the name of the relationship between the peak wavelength for a blackbody radiator and its temperature; what sort of relationship is it? Need a Hint? A) Planck's Law, luminosity = fourth power of the temperature. B) Bohr's Law; atoms will have quanitized electron states proportional to their temperature. C) Wein's Law; that the peak savelength is inversely propoertional to the body's temperature. D) Holmholtz Principle; as a body grows smaller, it must heat up.

Here we study how changes in temperature affect the energy radiated by the surfaces of planets. Given that the temperature of the surface of Venus is about 750 K, and that the surface of Mars is about 250 K, let's compare their infrared output.

 2 If the surface of Venus is, on average, about three times hotter than the surface of Mars, how does the infrared output of the two planets compare? Need a Hint? A) Venus gives off three times as much energy, but at about the same wavelengths. B) Mars gives off three times less energy, but at three times shorter wavelengths. C) Mars gives off about the same total amount of energy, but at three times longer wavelengths. D) Venus's infrared radation peaks at 1/3 that of Mars in wavelength, and far exceeds that of Mars in intensiry.

Any object warmer than absolute zero gives off some radiation, but its temperature determines how much energy it radiates, and in what forms. Here we study how changes in temperature affect the colors of stars.

 3 In what wavelength range does the 5,800 K temperature of the Sun's photosphere cause most solar radiation to fall? Need a Hint? A) ultraviolet B) visible C) infrared D) radio

Any object warmer than absolute zero gives off some radiation, but its temperature determines how much energy it radiates, and in what forms. Wein's Law is a math expression that allows us to quantatively calculate just where the peak will fall.

 4 Use Wein's Law to find the peak radiation for a star whose surface temperature is 2,900 K. In what form of energy would this peak fall? Need a Hint? A) 100, 000 nm in the microwaves B) 1,000 nm in the near infrared C) 100 nm in the ultraviolet D) 100 nm in the X-rays

Wein's Law applies to a wide range of bodies and temperatures. In the extreme case of collapsed stars, the temperatures can be very hot.

 5 A newly formed white dwarf has a peak in its spectrum at 145 nm, in the ultraviolet. Find its surface temperature. Need a Hint? A) 200 K B) 2,000 C) 20,000 K D) 200,000 K