Q. A tuning fork and a sonometer wire were sounded together and produce 4 beats per second. When the length of sonometer wire is $95\ cm$ or $100\ cm,$ the frequency of the tuning fork is
A) $156\ Hz$
B) $152\ Hz$
C) $148\ Hz$
D) $160\ Hz$
Explanation
(a) Probable frequencies of tuning fork be $n + 4$ or $n - 4$
Frequency of sonometer wire $n \propto \frac{1}{l}$
$\therefore\frac{n + 4}{n - 4} = \frac{100}{95}$ or $95(n + 4) = 100(n - 4)$
Or $95n + 380 = 100n - 400$ or $5n = 780$ or $n = 156$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.