ELECTRIC FIELDS IN MATTER — Edward Purcell & David Morin
Physics — E&M · em-waves-superposition
Problem
A sinusoidal wave is reflected at the surface of a medium whose properties are such that half the incident energy is absorbed. Consider the field that results from the superposition of the incident and the reflected wave. An observer stationed somewhere in this field finds the local electric field oscillating with a certain amplitude E. What is the ratio of the largest such amplitude noted by any observer to the smallest amplitude noted by any observer? (This is called the voltage standing wave ratio, or, in laboratory jargon, VSWR.)