Hey all, A physics example I'm working on to do some studying. The example is as follows: What is the wavelength of the scattered photon when a free electron (initially stationary) acquires maximum energy in a collision with a photon of energy 4 x 10^3 eV? My problem is this: it seems anything I do only deals with the photon of energy 4 x 10^3 eV. i.e. I can find the frequency using the relation E=hf and then lambda using lambda = c/f, but none of that relates to " lambda prime". Help? Thanks in advance.