An Electron-Positron Pair Traveling Towards Each Other with a Speed $\rarr$

Multiple Choice

An electron-positron pair traveling towards each other with a speed of 0.95 c with respect to their center of mass,collide and annihilate according to e^- + e⁺ $\rarr$ $\gamma$ + $\gamma$ .Assuming the observer is at rest with respect to the center of mass of the electron-positron pair,what is the wavelength of the photons?

A) 340 fm
B) 380 fm
C) 760 fm
D) 1200 fm
E) 2400 fm