Doppler Effect

Suppose a spectral line of hydrogen, normally at 500 nm, is observed in the spectrum of a star to be at 500.1 nm. 

How fast is the star moving toward or away from Earth?

ANSWER:

Because the light is shifted to a longer wavelength, the star is moving away from us:

ν = c × Δλ / λ = 299792458 m/s × 0.1 nm / 500 nm = 59 958.4916 m/s ≈ 6.00×10⁴m/s. 

Its speed is 60,000 m/s. 

To enter the numerical value of the ansver in scientific notation with 3 significant figures, type 6.00E4