One metre long sonometer wire is stretched with a force of 4kg wt, another wire of same material and diamter is arranged along a side. The second wire is stretched with a force of 16kg wt. if the length of the second wire is in its second harmonic is the same as fifth harmonic of the first wire, then the length of the second wire will be

Options

A. 40cm
B. 40cm
C. 80cm
D. 70cm

Answer

C

Explanation

`n_1 prop (sqrtT_1)/(l_1) " and " n_2 prop (sqrtT_2)/(l_2)`
`2n_2=5n_1`
`therefore (2xx4)/(l_2) = (5xx2)/(1)`
`therefore l_2= 0.8m`