RGU Question Paper Physics Semester VI 2020: Atomic Physics and Nuclear Physics

 

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BSc (VI Semester) Examination

PHYSICS

Paper : PHY–361 (New Course)

( Atomic Physics 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) Describe Rutherford atomic model on the basis of alpha scattering experiments. 8

(b) What are the objections raised against Rutherford atomic model? 2

2. (a) State and explain Sommerfeld’s theory of hydrogen atom. Why it cannot explain the fine structure of Ha-line? 6

(b) Calculate the longest and the shortest wavelengths in Lyman and Balmer series of hydrogen atom. 2+2=4

3. (a) Draw an energy-level diagram of sodium atom and using this, discuss the salient features of the spectra of alkali metals. 2+4=6

(b) Give reason why only principal series of lines exists in the absorption spectrum of alkali metal but not in the emission spectra. 4

4. (a) Explain splitting of D-lines of sodium by Paschen-Back effect. 4

(b) Obtain an expression for the change in energy in Paschen-Back effect. 6

5. (a) What are continuous and characteristic X-rays? 4
(b) State and prove Moseley’s law. Discuss its importance. 6

6. Write short notes on any two of the following : 5×2=10
(a) Raman effect
(b) Rayleigh scattering
(c) Pauli’s exclusion Principle

Section—B

( Nuclear Physics )

7. (a) Discuss briefly the meson theory of nuclear forces. 8
(b) Determine the range of nuclear force mediated by h having a mass corresponding to 550 MeV.

8. (a) Why do stable nuclei have more neutrons than protons? 4

(b) What are the achievements and failures of the liquid-drop model? 6

9. (a) Mention different components of nuclear reactor. 2

(b) Explain the function of moderator in uranium fed nuclear reactors. 4

(c) Calculate the energy released by fusion of 1 kg of $U^{235}$ in kWh if the energy released per fission is 100 MeV and Avogadro’s number is $6.03\times {10}^{23}$. 4

10. Discuss the working principle and construction of linear accelerator. Write its limitations. 8+2=10

11. (a) What are cosmic rays? Explain the latitude effects of cosmic rays. 2+4=6

(b) Discuss the properties of leptons in brief. 4

12. Write short notes on any two of the following : 5×2=10
(a) Symmetry and conservation of elementary particles
(b) Cyclotron
(c) Fission and fusion reactions