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An expression for oscillating electric field in a plane electromagnetic wave is given as E_z = 300 sin (5π × 10³ x - 3π × 10¹¹ t) Vm⁻¹. Then, the value of magnetic field amplitude will be (Given : speed of light in Vacuum c = 3 × 10⁸ ms⁻¹)

Asked in JEE Main 30th June 1st shift 2022 · E0 = cB0 and E/B = c

Answer: (2) 5 × 10⁻⁶ T

Step-by-step solution

k = 5π × 10³ rad m⁻¹ ω = 3π × 10¹¹ rad s⁻¹

v = ω/k = (3π × 10¹¹)/(5π × 10³) = 6 × 10⁷ m s⁻¹, so the wave is in a medium, not vacuum

B₀ = E₀/v = 300/(6 × 10⁷) = 5 × 10⁻⁶ T

Why the other options are wrong

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