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

Options

A. (a) `0.04s`
B. (b)`0.10s`
C. ( c ) `0.20s`
D. (d) `0.40 s`

Answer

B

Explanation

(b) KEY CONCEPT: The time required for constructive interference equal to the time period of a wave pulse.
For a string frequency `f = (1)/(2l) sqrt((F)/(m))`
:. Time period, `T = 2lsqrt((m)/(F))`
`F = 1.6N`, `m = (mass)/(length) = (10^(-2))/(0.4) = 2.5 xx 10^(-2)`
:. `T = 2 xx 0.4 sqrt((2.5 xx 10^(-2))/(1.6)) = 0.1 sec`.