## College Physics (4th Edition)

The wavelength measured by an observer on the Earth is $864~nm$
Let $\lambda_0 = 480~nm$ and let $\lambda'$ be the wavelength measured by an observer on the Earth. We can find the wavelength measured by an observer on the Earth: $\frac{\lambda'-\lambda_0}{\lambda_0} = \frac{v}{c}$ $\lambda'-\lambda_0 = \frac{v}{c}~\lambda_0$ $\lambda' = \frac{v}{c}~\lambda_0+\lambda_0$ $\lambda' = \frac{2.4\times 10^8~m/s}{3.0\times 10^8~m/s}~(480~nm)+(480~nm)$ $\lambda' = 864~nm$ The wavelength measured by an observer on the Earth is $864~nm$.