Question

A string of length $l$ between two bridges of a sonometer vibrates in first overtone. The amplitude of vibration is maximum at

• A. $\frac{l}{4}$ and $\frac{3l}{4}$
• B. $\frac{l}{2}$
• C. $\frac{l}{6},\frac{3l}{6}$ and$\frac{5l}{6}$
• D. can not say

Answer 1

The correct option is A $\frac{l}{4}$ and $\frac{3l}{4}$

as both edges are clamped, both are nodes
$l=\lambda$ as its in first overtone.
$\therefore$ points of maximum amplitude are $\frac{\lambda }{4}and\frac{3\lambda }{4}$
$\frac{l}{4}and\frac{3l}{4}$