A wave 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 of `10 cm `from the fixed end . The speed of the wave (incident and reflected) is

Options

A. ` 5 m//s`
B. ` 10 m//s`
C. ` 20 m//s`
D. ` 40 m//s`

Answer

C

Explanation

The fixed end is a node and the distance between this node and the adjacent node ` = 10 cm`.
This distance ` = lambda/2 :. lambda/2 = 10 cm " or " lambda = 20 ` cm
and ` v = n lambda = 100 xx 20/100 = 20 ` m/s