A galaxy in the constellation Ursa Major is receding from the earth at 15.000 km/s. If one of the character wavelength of the light the galaxy emits is 550 nm, what is the corresponding wavelength measured by the astronomers on the earth?
Solution:
Given:
v = 15.000 km/s = 1.5 × 107 m/s
c = 3 × 108 m/s
λ0 = 550 nm
λ = ?
β = v / c = − 0.05 ( − sign for receding)
Doppler Effect for light:
λ = 550 nm × √(1 + 0.05) / √(1 − 0.05) = 578 nm
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