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A laser beam of power 27 mW has a cross-sectional area of 10 mm 2 . The magnitude of the maximum electric field in this electromagnetic wave is given by [ Given permittivity of space ε 0 ≈ 9 × 10 - 12 C 2 N - 1 m - 2 , speed of light c = 3 × 10 8 m s - 1

Options

  1. A1 kV m - 1
  2. B1 . 4 kV m - 1
  3. C0.7 kV m - 1
  4. D2 kV m - 1

Correct answer

B. 1 . 4 kV m - 1

Step-by-step solution

I = P A = 1 2 ε 0 E 0 2 c ∴ E 0 = 2 P ε 0 CA = 2 × 27 × 10 - 3 × 36 π × 10 9 3 × 10 8 × 10 × 10 - 6 E 0 = 1 . 4 kV m - 1

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