Question

A wave frequency $100Hz$ travels along a string towards its fixed end. When this wave travels back after reflection, a node is formed at a distance of $10cm$ from the fixed end. The speed of the wave (incident and reflected) is

• A. $5m/s$
• B. $10m/s$
• C. $20m/s$
• D. $40m/s$

Answer 1

The correct option is C $20m/s$

Frequency of the wave $=100H_3$

$\therefore$ Time period $=\frac{1}{f}=\frac{1}{100}=0.01sec$

wavelength of the wave $=2\times 10cm=20cm$

$\lambda =0.2m$

Speed of the wave $V_w=\frac{w}{k}=\frac{2\pi /T}{2\pi /\lambda }=\frac{\lambda }{T}=\frac{0.20}{0.01}[V_w=20m/s]$

$\therefore$ Option (C) is correct.