Fine the wrong statement from the following :
The equation of a stationary wave is given by `y= 6 cos ((pi x)/(5)) sin (40 pix)`,where y and x are in cm and t is in second. Then for the stationary wave,

Options

A. Amplitude =3 cm
B. Wavelenghts =5 cm
C. Frequency = 20 Hz
D. Velocity =2 m/s

Answer

B

Explanation

` y = 6 cos ((pix)/5) sin (40 pi t)`
Comparing with
`y = 2A cos ((2pix)/lambda) sin ((2pit)/T)`
we get , `A = 3 cm, 2pint = 40pit :. N = 20 Hz`
` (2pi x)/lambda = (pi x)/5 :. lambda = 10 cm`
and `V = n lambda = 20 xx 10 = 2 `m/s
` [lambda = 5 ` cm is wrong ]