Waves - Result Question 28
28. A wave of frequency $100 Hz$ is sent along a string towards a fixed end. When this wave travels back after reflection, a node is formed at a distance of $10 cm$ from the fixed end of the string. The speeds of incident (and reflected) waves are
[1994]
(a) $5 m / s$
(b) $10 m / s$
(c) $20 m / s$
(d) $40 m / s$
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Answer:
Correct Answer: 28. (c)
Solution:
- (c) As fixed end is a node, therefore, distance between two consecutive nodes
$=\frac{\lambda}{2}=10 cm$.
$\lambda=20 cm=0.2 m$
As $v=n \lambda \therefore v=100 \times 0.2=20 m / s$
