LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Sc. DEGREE EXAMINATION – PHYSICS
FIFTH SEMESTER – APRIL 2008
PH 5500 - ATOMIC & NUCLEAR PHYSICS
Date : 28-04-08
Time : 1:00 - 4:00
Dept. No.
FG 21
Max. : 100 Marks
PART-A
Answer ALL questions.
(10x2=20 marks)
1. What are the limitations of Thomson’s parabola method?
2. Write down the electronic configuration of Na and Cl.
3. What is photo electric effect?
4. Calculate the work function of sodium in eV, given threshold wavelength is 6800Å.
5. Explain the terms: (i) Isotone
(ii) Isomer
6. Calculate the binding energy in Mev of deutron.
Given: Mass of 1 H 1  1.008145 & mass of 1 n1  1.008987 amu.
and mass of 1 H 2  2.014741 amu.
7. Why are neutrons moderated in nuclear reactors?
8. What are magic numbers?
9. What are cosmic rays?
10. Mention any two properties of nuclear forces.
PART-B
Answer any FOUR questions.
(4x7.5=30 marks)
11. Describe Franck-Hertz experiment for determining the critical potentials.
12. Describe L-S and J-J coupling schemes.
--(4+3.5)
13. a) Mention any five properties of gamma rays.
--(5)
b) Alpha particles from polorium travel along a semicircle of radius 20cm in a magnetic field of 1.763
wb/m2. Find the velocity and energy of the particles. e/m of   4.824 x107 ckg 1 and mass of
  6.643x1027 kg
14. Give an account of any three sources of neutron.
--(3x2.5)
15. a) Explain Yukawa’s meson theory of nuclear forces.
--(4)
b) How does the intensity of cosmic ray varies with attitude? --(3.5)
PART-C
Answer any FOUR questions:
(4x12.5=50 marks)
16. a) Explain the principle and experimental arrangement of stern-Gerlach in support of spatial
quantisation.
---(4+6)
b) Why it is necessary to use a beam of neutral atoms and not of ions in this experiment? ---(2.5)
17. a) Derive an expression for the change in wavelength of a pholon in complon scattering. ---(9)
b) Pholon of energy 1.02 MeV undergoes Compton scattering through 1800.Calculate the wavelength
of scattered pholon.
---(3.5)
18. a) Give the origin of the B-ray line and continuous spectrum. ---(5+5)
b) Calculate the binding energy of a neutron in the
7
6
3 Li  7.016004, 3 Li  6.015125
and 1
.
----(2.5)
0 n 1.008665
19. a) Derive the four factor formula for a thermal nuclear reactor. ---(9.5)
b) Calculate the energy released when 1 kg of U235 undegoes nuclear fission. Assume energy per
fission is 200 MeV.
---(3)
20. Obtain an expression for binding energy of a nucleus based on the semi-empirical mass formula
----(12.5)
1