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Problem 2 - Entrance Test

Two wave functions y₁ = 4sin(2x - t) and y₂ = 4sin(2x + t) superpose. What is the amplitude of the resultant standing wave at x = λ/4?

Correct: B

Superposition gives y = 8cos(2x)sin(t). At x = λ/4, cos(2x) = cos(π) = -1. Amplitude is |8cos(2x)| = 8. Hence, the maximum amplitude is 8.