The displacement of partcles in a string streched in the x-direction is by `y`. Among the following expressions for `y`, those describing wave motion are :

Options

A. `cos kx sin omega t`
B. `k^(2) x^(2) - omega^(2) t^(2)`
C. `cos^(2) (kx +omega t)`
D. `cos(k^(2) x^(2) - omega^(2)t^(2))`

Answer

A

Explanation

`y_(1)=cos kx omega t=(1)/(2)[sin (omega t +kx)+sin(omega t-kx)]`
(Stationary Wave)
`y_(3)=cos^(2)(kalpha+omegat)=(1)/(2)[1+cos2(kx+omegat)]`
(Progressive Wave).