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Question:

An electromagnetic wave of intensity 50 Wm⁻² enters in a medium of refractive index 'n' without any loss. The ratio of the magnitudes of electric fields, and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively, given by:

(1/√n, 1/√n)

(1/√n, √n)

(√n, 1/√n)

(√n, √n)

Solution:

C = 1/√(μ₀ε₀) V = 1/√(kε₀μ₀) [For transparent medium r ≈ ε₀]
∴ CV = 1/k = n
1/2ε₀kE²v = intensity = 1/2ε₀E²c
∴ E²/c = kE²v ⇒ E₀/E = √k = n
Similarly, B²/2μ₀c = B²/2μ₀v ⇒ B₀/B = 1/√n