NEET-XII-Physics
10: Wave Optics
- #11The 6563 Å
line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.
Ans : Wavelength ofline emitted by hydrogen,
λ = 6563 Å
= 6563 × 10-10 m.
Star’s red-shift,
Speed of light,
Let the velocity of the star receding away from the Earth be v.
The red shift is related with velocity as:
Therefore, the speed with which the star is receding away from the Earth is 6.87 × 105 m/s.