1.

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 pulses are produced at one end in equal intervals of times Deltat. the minimum value of Deltat, which allows constructive interference between successive pulses , is :

Answer»

0.05s
0.20 s
0.40 s
0.10 s

Solution :In a string VELOCITY of wave pulse is v= `SQRT((T)/(m))`
` v = sqrt(((1.6)/(10^(-2)))/(0.4)) = `8 m/s.
When the pulse is reflected at the end it suffers a phase chase of `pi`. Again with REFLECTION at other end it suffers a phase change of `pi`. so the original pulse is obtianed after two reflections . If wave is produced at that instantthem two waves interfere CONSTRUCTIVELY.
`therefore` MINIMUM time for the same is t `= (l + l)/(v)`
`= (0.4 + 0.4)/(8) = (1)/(10) = 0.1 ` s.
Correct choice is (d).


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