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Assume that a lamp radiates power P uniformly in all directions. The magnitude of electric field strength at a distance r from the lamp is

Options

  1. AP πcε 0 r 2
  2. BP 2 πcεr 2
  3. CP 2 πε 0 r 2 c
  4. DP πε 0 cr 2

Correct answer

C. P 2 πε 0 r 2 c

Step-by-step solution

Intensity, I = power area = P 4 πr 2 = average energy density × velocity = 1 2 ε 0 E 0 2 c ∴ E 0 = 2 P 4 πε 0 r 2 c = P 2 πε 0 r 2 c

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