A string of length `0.4 m` and mass `10^(-2)kg` is tightly clamped at its ends. The tension in the string is `1.6 N`. Identical wave pulse are produced at one end at equal intervals of time, `Deltat`. The minimum value of `Deltat` which allows constructive interference of successive pulse is

Options

A. `0.05 s`
B. 0.10 s`
C. `0.20 s`
D. `0.40 s`

Answer

B

Explanation

Velocity of wave : `v = sqrt((T)/(m)) = sqrt((1.6)/(10^(-2)//0.4))= 8 m//s`
The wave will be in same phase after travelling a distance of `2l = 2 xx 0.4 = 0.8 m`.
And constructive interference will take place. So time `Delta t`
`Delta t = (0.8)/(v) = (0.8)/(8) = 0.10 s`.