The phase difference between two points separated by 1m in a wave of frequency 120 Hz is `90^(@)` . The wave velocity is

Explanation

Distance between two points `Delta x = 1m` Frequency in = 120 Hz
Phase difference `phi = 90^(@) = 0 . 5 pi `
The relation for the phase difference is
`phi = (2pi)/(lambda) xx Delta x `
or `lambda = (2 pi xx Delta x)/(phi) = (2 pi x 1)/(0 . 5 pi) = 4 m `
The velocity of wave is given by
`u = n lambda = 120 xx 4 = 480 m//s `