Question

A string of length 0.4 m and mass 10^–2 kg is tightly clamped at its ends. The string is under tension 16 N. The minimum value of ∆t which allows constructive interference of successive pulse is 

(a) 0.05 s 

(b) 0.10 s 

(c) 0.20 s 

(d) 0.40 s

Answer 1

The velocity of the pulse down the string is

The pulse at A will come to A in the same direction after reflections at the end points D and C (Fig. 5.8), and meet the next pulse at A for constructive interference (see Chapter 12). Time taken by the pulse = 2 × 0.4/8 = 0.10 s. 

Correct Choice : b.