A string of length \(0.5\) m and mass \(10^{-3}\) kg is tightly clamped at its ends. The tension in the string is \(0.8\) N. Identical wave pulses are produced at one end at equal intervals of time \(\Delta t\). What is the minimum value of \(\Delta t\) which allows constructive interference between successive pulses?
Show Hint
Find the wave speed, then the round trip time between the clamped ends.
Step 1: Use standing wave idea
Constructive reinforcement means the pulse train matches the fundamental period $T_1=\frac{2L}{v}$ of the string. The fundamental frequency is $\frac{v}{2L}=20$ Hz, so the smallest interval is $\frac{1}{20}=0.05$ s.
Final Answer:
Option (D).
\[ \boxed{\text{(D)}} \]