1. The problem statement, all variables and given/known data Two equal energy photons collide head on and annihilate each other, producing a u+, u- pair. The two particles have equal mass, about 207 times the electron mass. A) Calculate the maximum wavelength of the photons for this to occur. B) If the wavelength calculated in A) is halved, what is the speed of each muon after they have moved apart (use the correct expressions for relativistic momentum and energy) 2. Relevant equations E = hc/lambda 3. The attempt at a solution I have solved part A) using the equation above, with the maximum wavelength occurring for the minimum energy (the rest energy of the muon pair) lambda max = hc/((3.394x10^-11)/2) = 1.17x10^14m I am having trouble finding the speed of each muon after they have moved apart... lambda = 5.855x10^-15 for each photon (from A)) then each photon has E = 3.394x10^-11J So through conservation of energy using E^2 = (pc)^2 + (m0c^2)^2 6.788x10^-11 = 2(pc + m0c^2) p = 5.656689x10^20 using p = (mv)/(1-v^2/c^2)^(1/2) rearrange to find p^2=v^2(m^2+(p^2/c^2)) rearrange to find v^2 and input the values of p, m and c where m = 207(9.109x10^-31) gives v = 0.709c where c is the speed of light This answer is wrong, but I can not see where I have made a mistake in calculation.