Question

A hydrogen line in a star's spectrum

Answer 1

Answer: V = 4.35 × 10^12 m/s

Explanation: To calculate Rigel velocity relative to us, we should use doppler effect formula.

Fo = (c ) / ( c - Vs) × f

Fo/f = (c ) / ( c - Vs)

4.26 × 10^10 = (3×10^8) 6.17×10^14/(3×10^8 - V)

4.26×10^10/6.17×10^14 = (3×10^8)/(3×10^8 - V)

6.9×10^-5 = (3×10^8)/(3×10^8 - V)

Cross multiply

20713.13 - 6.9×10^-5V = 3×10^8

Collect the like terms

6.9×10^-5V = 3×10^8 - 20713.13

6.9×10^-5V = 299979286.9

V = 299979286.9/6.9×10^-5

V = 4.3475 × 10^12 m/s

Therefore, Rigel's velocity relative to us is 4.3475 × 10^12 m/s