A 100 Hz source moves toward a wall at 20 m s⁻¹. O₁ and O₂ are stationary observers. Let f₁ and f₂ be the beat frequencies heard by O₁ and O₂ between the direct sound and the sound reflected from the wall. Take sound speed = 330 m s⁻¹. Which statement is correct?

Question

G1 Physics · Accepted Answer

Step 1: Use superposition at the boundary. Reflection from a denser/fixed boundary introduces phase reversal; from a free boundary it does not. Step 2: Energy ratio gives amplitude ratio through I ∝ A² for waves in the same medium. Step 3: Combine incident, reflected and transmitted waves with the proper direction. Final: C: f₁ > f₂.