A plane progressive wave is represented by the equation `y= 0.25 cos (2 pi t - 2 pi x)` The equation of a wave is with double the amplitude and half frequency but travelling in the opposite direction will be :-

Options

A. `y = 0.5 cos (pi t - pi x)`
B. `y = 0.5 cos (2 pi t + 2 pi x)`
C. `y = 0.25 cos (pi t + 2 pi x)`
D. `y = 0.5 cos (pi t +pi x)`

Answer

D

Explanation

`y_(1)=0.25cos(2pit-2pix)flamda=const`
`f=f//2rArr lamda=2lamda`
`y_(2)=2xx0.25cos((2pit)/(2)+(2pix)/(2))=0.5cos(pit+pix)`