Certain characteristic wavelength in the light from a galaxy in the constellation virgo are observed to be increased in wavelength, as compared with terrestrial sources, by about `0.4%`. What is the radial speed of this galaxy with respect to earth ? Is it approacing or receding ?

Answer

`1.2 xx 10^(6)ms^(-1)` ; receding

Explanation

The recession velocity,
`v_(s) = (Delta lambda)/(lambda) xx c = (0.4)/(100) xx (3 xx 10^(8)) = 1.2 xx 10^(6)m//s`