1. What is the highest frequency electromagnetic wave that would be considered an infrared wave? How much energy would be carried by one photon of this wave? Answer the same question for visible light, ultraviolet light, X-rays, and radiowaves.

  2. Would we want to make the reflecting surface of a telescope out of a blackbody? Why or why not? How warm would a blackbody have to be in order for lambdamax to be at the longest lambda of infrared light? Answer also for visible, ultraviolet, X-rays and gamma-rays.

  3. A spectral line of hydrogen is observed from a distant galaxy at a wavelength of 657.36 nm (1 nm = 10-9 meters). If this same spectral line is emitted by gas in our own galaxy, we observe it at a wavelength of 656.70 nm. What can you conclude from these facts?

  4. A galaxy recedes from us at 60% of the speed of light. By what factor must we multiply the wavelength of the photon emitted by the galaxy to get the wavelength as observed by us? What is the redshift z of this galaxy?

Evans's 324 | Astronomy Department