Two coherent waves, each having intensity I₀, superpose at a point with phase difference φ. Which expression gives the resultant intensity I?
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Question

Two coherent waves, each having intensity I₀, superpose at a point with phase difference φ. Which expression gives the resultant intensity I?

G1 Physics · Accepted Answer

For two coherent waves, I = I₁+I₂+2√(I₁I₂) cosφ. With I₁ = I₂ = I₀, we obtain I = 2I₀(1+cosφ). Using 1+cosφ = 2cos²(φ/2), I = 4I₀ cos²(φ/2). Correct option: B.