Q. A string of length 0.4m and mass $10^{- 2}$ kg is tightly clamped at the ends. The tension in the string is 1.6 N. Identical wave pulses are produced at one end at equal intervals of time$\mathrm{\Delta}t$. The minimum value of $\mathrm{\Delta}t$, which allows constructive interference between successive pulses is
A) 0.05 s
B) 0.10 s
C) 0.20 s
D) 0.40 s
Explanation
(b) Here, $m = \frac{10^{- 2}}{0.4}kgm^{- 1} = \frac{1}{40}kgm^{- 1}$,
$T = 1.6$
$v = \sqrt{T/m} = \sqrt{\frac{1.6}{1/40}} = 8ms^{- 1}$
Time interval, $\mathrm{\Delta}T = \frac{\lambda}{v} = \frac{2l}{v} = \frac{2 \times 0.4}{8} = 0.1s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.