A wave of frequency 100 Hz travels along a string towards its fixed end. When this wave travels back, after reflection, a node is formed at a distance 10 cm from the fixed end. The speed of the wave (reflected and incedent ) is :

Options

A. 5 `m^(-1)`
B. 20 `m^(-1)`
C. 100 `ms^(-1)`
D. 40 `ms^(-1)`

Answer

B

Explanation

here distance between consecutive nodes.
`(lambda)/(2) = 10 cm " " rArr " " lambda = 20 cm `
u = v `lambda = 100 x 20 = 2000 cm s^(-1) = 20 ms^(-1)`.
hence the correct choice is (b)