QP 50821 Page No... 1
Third Year B.Sc., Degree Examinations,
December 2017
(Directorate of Distance Education)
PHYSICS
Paper- III: DSC 210: Spectroscopy, Wave Mechanics Statistical
Mechanics, Relativity and Astrophysics.
Time: 3 hrs] [Max. Marks: 75/85
Instruction to the Candidates:
1. Students who have attended 25 marks IA scheme will have to answer for total 75
marks.
2. Students who have attended 15 marks IA scheme will have to answer for total of 85
marks.
3. Section E is compulsory for 85 marks scheme only.
SECTION A
I. Answer the following in a word, a phrase or a sentence: 10 x 1 10 Marks
1. What path does beam of electrons trace when an electric field is applied in a
direction perpendicular to the direction of motion of the beam of electrons?
2. Name any two uses of semi conductor laser.
3. What are white X rays?
4. State Hubble's law.
5. What is the effect of finite mass of nucleus on the atomic spectra?
6. Which method is employed to study the microscopic states of a system?
7. What is space quantization?
8. In which region the pure rotational spectrum of a molecule can be observed?
9. Is the concept of simultaneity has an absolute meaning?
10. Write the quantum mechanical operator for energy.
SECTION B
II. Answer any FIVE of the following questions: 5 x 3 15 Marks
11. Write a note on Rutherford's model of the atom.
12. Find the value of the ratio of mass of proton to that of electron. Given:
Rydberg constant of hydrogen atom =1.096777×107 m
Rydberg constant of Helium atom =1.097224×107 m
13. Explain the fine structure of sodium D lines.
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QP 50821 Page No... 2
14. State and explain the significance of Mosley's law.
15. Write a note on Minkowski's world.
16. Can matter waves travel faster than light? Justify.
17. Write a note on H R diagram.
SECTION C
III. Answer any FIVE of the following questions: 5 x 6 30 Marks
18. Give the quantum mechanical explanation of normal Zeeman effect. Illustrate
with p state.
19. State and derive the Bragg's law of X ray diffraction.
Write any four applications of X rays.
20. Deduce the Planck's law of radiation from B E statistics.
21. Write a note on Neutran stars and Black holes.
22. What is Raman effect? Describe the experimental study of Raman effect.
23. Distinguish between inertial mass and gravitational mass. Explain, any two
experimentally observed facts which supports the Einstein's general theory of
relativity.
24. Give the theory of pure rotational spectrum of a diatomic molecule.
SECTION D
IV. Answer any TWO of the following questions: 2 x 10 20 Marks
25. Describe the construction and working of Ruby laser.
The wavelength of He Ne laser is 6328Å. Its output power is 3.147mW.How
many photons are emitted per minute when it is in operation.
26. Explain the quantum numbers associated with vector atom model.
Calculate the longest and shortest wavelength of the Balmer series of the hydrogen
atom. Rydberg constant of hydrogen atom =1.097×107 m .
27. Obtain the Schrodinger's equation for a particle in a one dimensional box and solve
it to obtain the energy eigen values.
The position and momentum of 1 KeV electron are simultaneously determined and
its position is located within 4 Å. What is the percentage of uncertainty in its
momentum?
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QP 50821 Page No... 3
28. Write a note on Spin orbit interaction ii) Rayleigh scattering.
A proton has a wavelength of 0.5Å. Calculate its energy in eV.
SECTION E
V. Answer any ONE of the following questions: 1 x 10 10 Marks
(Compulsory question for 85 marks scheme only)
29. Describe the Michelson Morley experiment. Also comment on the null result of
the experiment.
Show that a particle of zero rest mass should move with the speed of light in
vacuum.
30. State Heisenberg's uncertainty principle. Illustrate it with the g − ray microscope
experiment.
Calculate the minimum voltage that should be applied to an x ray tube to
produce x ray photons of wavelength 0.1Å.