PH 253 Midterm: PH253_ex1_practice_answers
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Exam 1 practice problems: answers & some solutions: an electron moving initially with constant speed v is brought to rest with uniform deceleration a lasting for a time t = v/a. Compare the electromagnetic energy radiated during the deceleration with the electron"s initial kinetic energy. Express the ratio in terms of two lengths, the distance light travels in time t and the classical electron radius, re = mec2 . Recall the larmor formula, which gives the total power radiated from an accelerating charge (v c): Solution: the acceleration is a = v/t, so we can nd the radiated power readily. After the time t required to decelerate completely, the radiated energy is e = p t and the initial kinetic energy of the electron is 1. The time light travels in time t is rl = ct. Using the de nition of the classical electron radius above,
