Two waves of wavelength 40 cm and 42 cm produce 15 beats `s^(-1)`. The velocity of sound will be

Options

A. `340 ms^(-1)`
B. `332 ms^(-1)`
C. `126 ms^(-1)`
D. `306 ms^(-1)`

Answer

C

Explanation

`n_(1) - n_(2) = 15 "Beat"//s^(-1)`
`rArr (V)/(0.4) - (V)/(0.42) = 15` where, V: speed of sound
`rArr :. V [(0.42 - 0.4)/(0.42 xx 0.4)] = 15`
`:. V = (15 xx 0.42 xx0.4)/(0.02) = 126 m//s^(-1)`