# The Andromeda galaxy is moving toward us at 3.01x105 m/s. By how much will the frequency of the 6.17x1014 Hz hydrogen?

The Andromeda galaxy is moving toward us

at 3.01x105 m/s. By how much will the

frequency of the 6.17x1014 Hz hydrogen line

be shifted in the galaxy's spectrum

3.01 × 10^5 and 6.17 × 10^14

### 1 Answer

- SpacemanLv 71 year ago
The velocity v is positive for motion away from an observer and negative for motion toward

an observer. In terms of source frequency and observed frequency, this equation can be

written as

f(o) = f(s) x √[(1 - v/c)/(1 + v/c)]

c = velocity of light = 3.00E+05 km/s = 3.00E+08 m/s

v = velocity of the Andromeda Galaxy = -3.01E+05 m/s (negative for motion toward an observer)

f(s) = frequency of the source = 6.17E+14 Hz

f(o) = observed frequency = to be determined

Δf = change in frequency = to be determined

f(o) = 6.18E+14 Hz

Δf = f(o) - f(s)

Δf = 6.19E+11 Hz