A laser with a power of 1.0 mW has a beam radius of 1.0 mm. What is the peak value of the electric field in that beam? (c = 3.0 x 10⁸ m/s, μ₀ = 4π × 10^-7 T ∙ m/A, ε₀= 8.85 × 10^-12 C²/N ∙ m²) A) 490 V/m B) 840 V/m C) 65 V/m D) 120 V/m E) 22 V/m

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Quizplus · Accepted Answer

The intensity I of the laser beam is given by I = P/A, where P is the power and A is the area of the beam. The area A = πr², where r is the radius. The intensity is also related to the electric field E by I = (1/2)ε₀cE². Solving for E gives E = sqrt(2I/ε₀c). Substituting the given values, E = sqrt(2 * (1.0 x 10^-3 W) / (π * (1.0 x 10^-3 m)²) / (8.85 x 10^-12 C²/N·m² * 3.0 x 10^8 m/s)) ≈ 490 V/m.

A Laser with a Power of 1