In the spectrum of light coming from a star, the Hα emission line is found to be shifted toward the red end of the spectrum. In the rest frame of the source object, the H line has a frequency of Hz. In the rest frame of Earth, the H line appears at Hz. If all of this redshift is due to relativistic motion of the star relative to Earth, how fast is the star moving away from Earth? Give your answer to 3 significant figures as a multiple of the speed of light.
If you drive fast enough toward a red light, because of the relativistic Doppler effect, it will appear green. If a driver on a road drives fast enough toward a set of traffic lights, instead of seeing a red light, he will see a green light. How fast does the driver have to travel in order for the red light, with a wavelength of 650 nm, to appear green, with a wavelength of 520 nm? Give your answer, in kilometers per hour, to 3 significant figures.
A spaceship is traveling from Earth to Epsilon Eridani. Every hour, the spaceship sends a transponder signal back to Earth. At what speed would the spaceship have to be traveling relative to Earth for the transponder signal to have a frequency in the rest frame of Earth that is of the frequency of the signal in the rest frame of the spaceship?