The phase difference between two points separated by 0.8 m in a wave of frequency 120 Hz is `90^(@)` . Then the velocity of wave will be

Options

A. `720 ms^(-1)`
B. `384 ms^(-1)`
C. `250 ms^(-1)`
D. `1 ms^(-1)`

Answer

B

Explanation

It is given that `v=120` Hz, phase difference, `Delta phi=pi/2` and path difference, `Delta x=0.8 m`.
As `Delta phi =(2pi)/lambda . Delta ximplies lambda =(2pi)/(Delta phi). Delta x=(2pi xx 0.8)/(pi//2)=3.2 m`
Hence, wave velocity, `v=v lambda =120xx3.2=384 ms^(-1)`.