Question 6 [2+3+2]

Obtain an expression for the Nuclear Size of an atom by solving for distance of closest approach (r) which is also known as Impact Parameter (say l). Use an incoming alpha-particle of mass mα and charge q that’s deflected by the presence of a nucleus of atomic number Z to obtain l. Now replace the variables by some numerical: mα = 6.8×10-27kg, e = 1.6 x 10-19 coul, Z=14, and vα= 2.0×107 m/s. Express the answer in Femto-meters.

Question 7 [3+4]

A proton has a radius R and the charge Q is uniformly distributed. Use Bohr’s atomic energy level formula for the 1st excited state {n=2} energy of the Hydrogen-atom.