Question

Q.10. (A) Find the radius of nucleus of an atom having atomic mass number equal to 125.
(B) Find the distance of closest approach when an a particle is projected towards the nucleus of silver atom having speed V. (mass of $\alpha$ particle $m_{\alpha }$)

Answer 1

Dear Student,
10A

Radius of Nucleus is calculated using formula :- R= R₀A^{1 /3} where R₀ = 1.2 x 10^-15m

Putting the value of A(mass number) in formula : R = 1.2 x 10^-15m x (125)^1/3
= 1.2 x 10^-15m x 5
= 6 x 10^-15m

10.B
$$\begin{gathered} edis\tan ceofclosestapproachisgivenasunder: \\ r0=\frac{1}{4\pi \epsilon 0}\times \frac{2\times Z\times e^2}{KE} \\ KE\hspace{0.17em}=\frac{M{V}^2}{2} \end{gathered}$$
Z for silver = 108
by putting the value of KE in term of velocity V we can calculate the distance of closest approach

Regards