Question

A string is stretched between fixed points separated by 75cm. It is observed to have resonant frequencies of 420Hz and 315Hz. There are no other resonant frequencies between these two. Then, the lowest resonant frequency for this string is
(a) 10.5Hz 

(b) 105Hz

(c) 1.05Hz 

(d) 1050Hz.

Answer 1

(b) : Let the successive loops formed be p and (p + 1) for frequencies 315Hz and 420Hz