A sound wave of frequency 100 Hz is travelling in air. The speed of sound in air is `350 ms^-1` (a) By how much is the phase changed at a given point in 2.5 ms ? (b) What is the phase difference at a given instant between two points separated by a distance of 10.0 cm along the direction of propagation ?

Explanation

`f = 100 Hz, v = 350 m//s`
`v = f l`
`350 = 100 lambda rArr 3.5 m`
(a) Phase difference
`phi = (2pi)/(T) Delta t = 2pi f Delta t`
`=2pi xx 100 xx 2.5 xx 10^(-3) = (pi)/(2)`
(b) `phi = (2pi)/(lambda) Delta x = (2pi)/(3.5) xx 0.1 = (2pi)/(35)`