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

Options

A. `480 m//s`
B. `180 m//s`
C. `720 m//s`
D. `240 m//s`

Answer

A

Explanation

`Delta x= 1 m Delta varphi=90^(@)=(pi)/(2) "rad", gamma =12 Hz`
As `Delta varphi =(2pi)/(lambda)xx Delta x`
(or) `(pi)/(2)=(2pi)/(lambda)xx1`
(or) `lambda=4m`
`v= gamma lambda120xx4= 480 m//s`