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A ball of radius R=50 cm is located in a non- magnetic medium with permittivityepsilon=4.0 . In that mediuma plane electromagnetic wave propagates, the strength amplitude of whose electri component is equal to E_(m) = 200 V //m. What amount of energy reaches the ball during a time interval t=1.0 min ? |
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Answer» Solution :For the Poynting vector we can derive as `lt S gt = (1)/(2) sqrt((epsilon epsilon_(0))/(mu_(0))) E_(m)^(2)` along the DIRECTION of propagation. Hence in time `t`(which is much longer than the time period `I` of the wave, the enegry reaching the BALL is `piR^(2) XX (1)/(2) sqrt((epsilon epsilon_(0))/(mu_(0))) E_(m)^(2)XXT = 5 kJ`. |
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