1. The problem statement, all variables and given/known data I am told that to a stationary observer, the lights infront of a spaceship has the wavelength = 480 nm when it arrives, and the lights in the back have wavelength 640 nm when the ship is moving away. Both lights (front and back) are the same. I have to find the wavelength of the two lights. 3. The attempt at a solution I have tried to use T = T_0 * (1+w/c)/sqrt(1-w^2/c^2) and from there use T-T_1 ... so the w's would go out, but they don't. When the spaceship is arriving, the speed is v - when it is moving away, it is -v. From there, I tried the above. How do I find the wavelengths? (I have to calculate relativistic).