Two identical sinusoidal sound waves of frequency and amplitude arrive at a point in air

PHYSICS · Single correct · A Level · Physics · Waves · Waves

Problem

Two identical sinusoidal sound waves of frequency

400\,\text{Hz}

and amplitude

2.0\,\text{mm}

arrive at a point in air. The displacement–time graphs at that point indicate that the second wave lags behind the first by

90^{\circ}

. What is the resultant amplitude at that point? (a)

4.0\,\text{mm}

(b)

2.8\,\text{mm}

(c)

1.4\,\text{mm}

(d)

2.0\,\text{mm}