A string is clamped at both the ends and it is vibrating in its `4^(th)` harmonic. The equation of the stationary wave is `Y=0.3 sin ( 0.157 x) cos (200 pi t)`. The length of the string is: (All quantities are in SI units.)

Options

A. 60m
B. 20m
C. 80m
D. 40m

Answer

C

Explanation

Clearly `(2x)/(lambda) = 0.157` `therefore lambda = 40m`
Hence for 4th harmonic, `1 = 4 xx (lambda)/(2) = 80m`