An alpha particle with kinetic energy `10 Me V` is heading toward a stationary tin nucleus of atomic number 50. Calculate the distance of closest approach (Fig . 3.23).
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Explanation

In approaching the nucleus, kinetic energy of alpha particle is coverted into electrical potential energy. So if r is the distance of the closest approach, then
`(1)/(2) m v^2 = (1)/(4 pi epsilon_0) (q_1 q_2)/( r)`
or `r = (1)/(4 pi epsilon _0) ((2 e)(50 e))/((K "inetic Energy"))`
or `r = (9 xx 10^9)((2 xx 1.6 xx 10^-19)(1.6 xx 10^-19 xx 50))/((10 xx 10^6 xx 1.6 xx 10^-19))`
=`14.4 xx 10^-15 m = 14.4 f m`.