Atomic and Nuclear Physics Answers

1.from the basics principles of bohr atomic model, drive an expression for the energy of hydrogen atom. use standards values in SI units to compute that energy and show that it is quantized.

2.compute the energy of hydrogen atom in its first excited state.

Give possible shell model nucleon configurations which could produce

the



2

5

,



2

1

and



2

1

excited states of

O

17

8 .

A narrow beam of 100 MeV neutrons, with a intensity 10 to the power 5

n/cm2

.s , is

normally incident on an aluminum foil. The elastic scattering cross

section of aluminum for 100 MeV neutrons is 0.95 barns. The density of

aluminum is 2.7 g/cm3

. How thick must the aluminum foil be in order to

reduce the number of unscattered neutrons emerging from the foil by

three orders of magnitude?

The sum of a number of proton and neutron is called:

A. Atomic number

B. Mass number

C. Isotopes

D. None of these

1. What is the number of a neutron in the nucleus of uranium:

A. 94

B. 145

C. 235

D. Same number

E. Different for different isotopes

An X-ray line of wavelength 0.53832A0 is found to be emitted from an X− ray tube with (Z= 30) target in addition to the characteristic Kα line of Zinc of wavelength 1.43603A0 . If the unkown line is due to an impurity in the target, obtain the atomic number of the impurity.

The Hydrogen atom in its ground state is excited by means of a monochromatic radiation of wavelength 970.6A0 . How many different wavelengths (transitions) are possible in the resulting emission spectrum ? [NB: you have to represents them on a diagram]. Find the longest wavelength amongst these.

The cross section of 113Cd for capturing thermal neutrons is 2 × 104 b (b= barns). The mean atomic mass of natural Cadmium is 112u and its density is 8.64 × 103 kgm−3 . Considering that 113Cd constitute 12% of natural Cadmium and if the fraction of incident (beam) of thermal neutrons that is absorbed is 0.01. Find: (a) The thickness of Cadmium needed for neutrons absorption

(b) The mean free path of thermal neutrons.

a) By applying the laws of conservation of energy and momentum, show that the K.E of αparticle radiated (during α-decay) is given by. T α = Q(A − 4) A ; where Q represents the energy available in the decay and A, the mass of the parent nucleus.

(b) Show that 236 94 P u is unstable and will spontaneously decay into 232 92 U. Consider: 236 94 P u = 236.046071u; 232 92 U = 232.037168u; 4 2He = 4.012603u.

In the absence of an external magnetic field, a transition frequency ν0 is observed between two energy levels of an atom. Show that in the presence of an external uniform magnetic field, the normal Zeeman effect is observed and the original transition generates into three transitions of frequencies: ν = ν0 −  eB 4πm ; ν = ν0; ν = ν0 +  eB 4πm where m is the mass of the electron.