A stationary wave is represented by y = A sin (100 t) cos (0.01 x) , where y and A are in millimetres , t is in second and x is in metre. The velocity of the constituent wave is

Options

A. the wave is a standing wave
B. the speed of the wave is 50/7 `ms^(-1)`
C. the frequency of oscillation is `500xx2piHz`
D. two nearest points in the same phase have separation `20 pi//7 cm`.

Answer

B

Explanation

`omega=500=2pif`
`= f=500/(2pi)`
`K=70 =(2pi)/(lambda)`
`rArr lambda=(2pi)/70`
velocity `=lambdaf=(2pi)/70xx500/(2pi)=50/7 m//s`
and `lambda=(2pi)/70 m`