Vibrations and Waves · Problem 3-16

Forced vibrations and resonance — A.P. French

Physics — Waves · radiating-electron-oscillator

Problem

According to classical electromagnetic theory an accelerated electron radiates energy at the rate Ke2a2/c3Ke^2a^2/c^3, where K=6×109K = 6 \times 10^9 N−-m2^2/C2^2, e=e = electronic charge (C), a=a = instantaneous acceleration (m/sec2^2), and c=c = speed of light (m/sec). (a) If an electron were oscillating along a straight line with frequency ν\nu (Hz) and amplitude AA, how much energy would it radiate away during 1 cycle? (Assume that the motion is described adequately by x=Asin⁡2πνtx = A \sin 2\pi\nu t during any one cycle.) (b) What is the QQ of this oscillator? (c) How many periods of oscillation would elapse before the energy of the motion was down to half the initial value? (d) Putting for ν\nu a typical optical frequency (i.e., for visible light) estimate numerically the approximate QQ and ``half-life'' of the radiating system.

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