In hydrogen spectrum the wavelength of line is 656 nm

PHYSICS · Single correct · A Level · Physics · Astrophysics · Astrophysics

Problem

In hydrogen spectrum the wavelength of

H_\alpha

line is 656 nm, whereas in the spectrum of a distant galaxy,

H_\alpha

line wavelength is 706 nm. Estimate the speed of the galaxy with respect to earth. (1)

2 \times 10^8

m/s (2)

2 \times 10^7

m/s (3)

2 \times 10^6

m/s (4)

2 \times 10^5

m/s