A wave representing by the equation `y = a cos(kx - omegat)` is suerposed with another wave to form a stationary wave such that point `x = 0` is a node. The equation for the other wave is

Options

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

Answer

C

Explanation

Since the point ` x = 0` is a node and reflectiion is taking place from point ` x = 0` . This means that reflection must be taking place from the fixed end and hence the reflected ray must suffer an additional phase change of `pi` or a path change of `lambda//2`.
So , If `y_("incident") = a cos (kx - omega t)` , then
`y _("reflected") = -a cos (omega t + kx)`