A galvanometer has resistance `36Omega` if a shunt of `4Omega` is added with this, then fraction of current that passes through galvanometer is:

Answer

4

Explanation

After `1^(st)` collision
`-(2)/(sqrt5) sqrt(2gl) = sqrt(2gl (1 - cos theta))`
`"cos" theta (1)/(5)`
Fro `II^(nd)` collision
`(2)/(sqrt5) . (2)/(sqrt5) sqrt(2gl) = sqrt(2gl (1 - cos theta))`
For `n^(th)` collision
`((2)/(sqrt5))^(n) = sqrt(1 - cos theta) rArr ((4)/(5))^(n) = 1 - cos theta`
`"cos" theta = 1 - ((4)/(5))^(n)`
Put `n = 0, 1, 2, 3` and get answer