I'm trying to solve this question for an assignment, and wanted to know if i am on the right route. An electron with given energy emits two bremmstrahlung photons and after the second emission it comes to rest. The relationship between the wavelengths (lamda1, lamda2) of the two emiited photons is given. Here is what i'm doing: K.E of electron = hc/lamda1 + hc/lamda2 and using the wavelength relationship, i find each lamda. Now how would i use them to calculate the energy of the electron between decelerations?