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A laser beam has intensity of 4.0 10¹⁴ ~W / m ² . The amplitude of magnetic field associated with beam is _ _ _ _ T. (Take _ o =8.85 10⁻¹² C ² / Nm ² and c =3 10⁸ ~m / s )

Options

  1. A18.3
  2. B1.83
  3. C5.5
  4. D2.0

Correct answer

B. 1.83

Step-by-step solution

The intensity of an electromagnetic wave is I = 1 2 ₀ c E₀^2 . From the relation E₀ = c B₀ , we get I = 1 2 ₀ c^3 B₀^2 . Solving for magnetic field amplitude: B₀ = 2I ₀ c^3 = 2 4.0 10¹⁴ 8.85 10⁻¹² (3 10^8)^3 = 8.0 10¹⁴ 2.39 10¹⁴ = 3.347 = 1.83 T.

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