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. `10.5 Hz`
B. 105 Hz
C. `1.05 Hz`
D. 1050 Hz

Answer 1

Correct Answer - D
`AB=sqrt(2)cm`
From refraction at air-water boundary,
`(1)((1)/(sqrt(2)))=(sqrt(2))sintheta" or "theta=30^(@)`
`thereforeBC=(sqrt(3))/(sqrt(2))cm`