Question

A string is stretched between fixed points separated by `75.0cm`. It is observed to have resonant frequencies of `420 Hz` and `315 Hz`. There are no other resonant frequencies between these two. Then, the lowest resonant frequency for this string is
A. `105 Hz`
B. `155 Hz`
C. `205 hz`
D. `10.5 hz`

Answer 1

Correct Answer - A
Two consecutive resonant frequencies for a string fixed at both ends will be
`(nv)/(2l)` and `((n+1)v)/(2l)`
`implies((n+1)v)/(2l)-(nv)/(2l)=420-315`
`implies(v)/(2l)=105Hz`. Which is the minimum resonant frequency.