An `alpha`- particle moving with initial kinetic energy K towards a nucleus of atomic number z approaches a distance 'd' at which it reverse its direction. Obtain the expression for the distance of closest approach 'd' in terms of the kinetic energy of ` alpha`- particle K.

Explanation

`K=(10)/(4piepsilon_0) (2e.ze)/(d^2)`
` d^2=(2ze^2)/(4piepsilon_0K)rArr d=sqrt((2ze^2)/(4piepsilon_0K))`