Path difference causes destructive interference for sound minima Steps: - Reflected sound travels extra path 2D; minimum intensity when 2D = (2n+1)λ/2 due to phase reversal at metal plate. - Consecutive minima occur when path difference increases by λ, so 2ΔD = λ, and ΔD = λ/2. - Microphone at first minimum D = 15.0 cm; moved away to next minimum, ΔD = 2.95 cm = 0.0295 m. - Wavelength λ = 2 × 0.0295 = 0.059 m. - Frequency f = v/λ = 330 / 0.059 = 5600 Hz. Why C is correct: - Matches f = v / (2ΔD) from interference condition for reflected waves, where ΔD is spacing between minima. Why the others are wrong: - A: Assumes ΔD = 15.0 m (units error), giving λ = 30 m, f = 11 Hz (too low). - B: Assumes ΔD = 1.5 m (scale error), giving λ = 3 m, f = 110 Hz (too low). - D: Assumes path difference ΔD (forgets factor of 2), giving λ = 0.0295 m, f = 11200 Hz (double the correct …