In the laboratory, one of the lines of sodium is emitted at a wavelength of 590.0 nm. When observing this light from a particular galaxy, however, this line is seen at a wavelength of 602.0 nm. We have to calculate the distance to the galaxy, assuming that Hubble’s law holds.

Solution:             Click For PDF Version

The relativistic Doppler shift formula is

.

Light of wavelength 590.0 nm is observed to be 602.0 nm. Therefore, the speed of the source can be obtained from the equation

The Hubble’s law is

Therefore, the distance of the galaxy as calculated using the Hubble’s law will be