JUNE-2021
B. Sc. (VI Semester) Examination
PHYSICS
Paper: PHY-361 (Old Course)
(Atomic and Nuclear Physics)
Full Marks : 80
Pass Marks : 35%
Time : Three Hours
Note: 1. Answer any four questions from Section – A, and any four questions from Section – B.
2. The figures in the margin indicate full marks for the questions.
Section – A
(Atomic Physics)
1. (a) State any two limitations of Bohr’s theory. 1
(b) State Pauli’s exclusion principle. 2
(c) What is Raman effect? Describe how Roman spectra can be observed experimentally. 2+5= 7
2. (a) State Moseley’s law. 2
(b) What are x-rays? Explain briefly how characteristic x-ray spectra with energy level diagram can be produced. 1+7= 8
3. (a) What is electron spin? 1
(b) Write Ray High Scattering formula. How does Ray High Scattering formula explain the blue colour of the sky? Write limitations of Ray High Scattering. 1+2+1= 4
(c) What is normal Zeeman effect? The Zeeman components of a 500 nm spectral lines are 0.012 nm apart when one Tesla of magnetic field is applied. Determine e/m value of electron. 5
4. (a) Write the statement of Ritz-combination principle show that the Ritz-combination principle is satisfied by the longest wavelength of Balmer series and the longest two wavelengths of the Layman series. 1+5= 6
(b) Find the wavelength of the transitions from =3 to = 2 and = 4 to = 2. To which series do these transitions belong? 4
5. (a) With a neat diagram of energy level diagram of Sodium atom, explain the salient features of the Spectra of alkaline metals. 6
(b) Describe the splitting of D-lines of Sodium by Paschen-Back effect. 4
6. Write any two short notes on the following: 5x2- 10
(a) Stern-Gerlach experiment
(b) Compton effect.
(c) Bohr-magneton
Section – B
(Nuclear Physics)
7. (a) What do you mean by ‘Saturation’ of nuclear forces? 2
(b) What are cosmic rays? Write their probable origins. 1+2= 3
(c) Explain how the asymmetry and pairing energy terms arise in the semi-empirical mass formula. 5
8. (a) Describe briefly the working principle of a GM counter. Give one of its drawbacks. 5
(b) Explain about the nuclear fusion and fission from the picture of binding energy curve. 5
9. (a) Describe how nuclear parity and nuclear spin can be predicted on the basis of the Shell Model. 5
(b) Explain the liquid drop model of the nucleus. 5
10. (a) Discuss the different terms in the Weizsacker formula. 6
(b) What are the general characteristics of nuclear forces? 4
11. (a) Explain the significance of magic numbers. 2
(b) Describe the Quarles model of hadrons including the properties of Quarles. 8
12. Write any two short notes on the following: 5x2= 10
(a) Spin-orbit interaction.
(b) Extensive-Air shower
(c) Yukawa meson theory
