RGU Question Paper Physics Semester VI 2021: Atomic Physics and Nuclear Physics (New)

 JUNE-2021

B. Sc. (VI Semester) Examination

PHYSICS

Paper: PHY-361 (New 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) Flow does nuclear spin effect the electronic spectrum of an atom? 2

(b) Explain briefly how the quantum numbers associated with vector atom model arise. 8

2. (a) Write two drawbacks of the Rutherford’s nuclear atom model. 2

(b) Discuss non-relativistic Sommerfeld theory of hydrogen atom. 8

3. (a) Why does the planetary model of an atom fail? 2

(b) Why does spin of an electron play an important role in the structure of energy levels of a many electrons but not in hydrogen atom? 2

(c) Describe briefly the Stern-Gerlach experiment. 6

4. (a) What is Rydberg constant? Determine the wavelength of Hα and Hβ lines of the hydrogen spectrum in the visible region. 1+2= 3

(b) State the postulates of the Bohr’s atom model. Derive an expression for the energy of the hydrogen atom in the nth orbit. Write the significance of the negative sign in the energy term. 2+4+1= 7

5. (a) Explain how an x-ray spectrum is produced. Which element has a $K_{\alpha }$ x-ray line of wavelength of 0.18 nm? 4+1= 5

(b) Explain experimental arrangement for the normal Zeeman effect to determine the Zeeman shift. 5

6. Write any two short notes on the following: 5x2= 10

(a) Ray High Scattering

(b) Pauli’s exclusion principle

(c) Compton effect

Section – B

(Nuclear Physics)

7. (a) How does binding energy value affect the stability of the nucleus? 2

(b) What are magic numbers? 2

(c) Explain briefly the Meson theory of Yukawa. 6

8. (a) Explain about Baryon and Lepton numbers. 2

(b) Describe briefly the working principle of GM counter. 3

(c) Distinguish between the nuclear fission and nuclear fusion process. 5

9. (a) Differentiate between neutrinos ad antineutrinos. 2

(b) Why must the quarks in a hadron have different colours? 2

(c) Discuss the four fundamental interactions. 6

10. (a) Distinguish between primary and secondary cosmic rays. 2

(b) Describe the construction and working principle of gas filled detectors. 8

11. (a) Find the energy release if two 1$H{e}^2$ nuclei fuse together to form 2$H{e}^4$ nucleus. (Given that B.E. per nucleon of 1$H{e}^1$ is 1.1 MeV and of 2$H{e}^4$ is 7.0 MeV) 2

(b) A cyclotron in which the magnetic flex density of 2.0 weber/$m^2$ is employed to accelerate protons. How rapidly should the electric field between the Dees be reversed? (Given that proton mass = 1.6x${10}^{-27}$ kg and charge = 1.6x${10}^{-19}$ C) 2

(c) If alpha particles are scattered from gold foil (A=97). At what minimum kinetic energy of the alpha particle will be deviated significantly from those predicted by Rutherford Scattering formula? 3

(d) Estimate α-decay energy of ${90}^{th 218}$ from the semispherical formula. 3

12. Write any two short notes on the following: 5x2= 10

(a) Spin-orbit interaction

(b) Ionization-Chamber

(c) East-west effect on cosmic rays.