Two whistles emit steady notes of frequencies and

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

Problem

Two whistles emit steady notes of frequencies

380\,\text{Hz}

and

385\,\text{Hz}

. The displacement of air at the listener’s position is a maximum at

t=0\,\text{s}

. At what earliest later time will the displacement again be a maximum? (a)

2.6\times10^{-3}\,\text{s}

(b)

0.20\,\text{s}

(c)

0.10\,\text{s}

(d)

0.40\,\text{s}