Q. 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
A) $5ms^{- 1}$
B) $10ms^{- 1}$
C) $20ms^{- 1}$
D) $40{ms}^{- 1}$
Explanation
(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 $v = v\lambda$
$\therefore\ \ \ \ \ v = 100 \times 0.2 = 20\ ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.