# Physics Paper V Atomic Physics Previous Year Question Paper Year 2005 : IIIrd Year

**Q. 1.** Derive Rutherford’s scattering formula for the scattering of alpha particles by heavy nuclei. Discuss its experimental verification.

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**Q. 2.** What is Compton effect ? What is its basic importance? Obtain an expression for Compton shift.

An X-ray photon of wave length 0.15° A is reflected at an angle of 135° after collision with an electron. Calculate the energy it loses on collision.

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**Q. 3. **What are limitations of Thomson’s parabola method for determining e/M of positive rays. Describe in detail. Aston’s mass spectrograph.

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**Q. 4. **Describe Millikan’s oil drop method for the determination of charge of electron. What is quantisation of charge ?

Fn Millikan’s oil drop experiment an oil drop of mass 4.9 * I0-14Kgm is balanced by applying a potential difference of 2 KV between two plates which are 8 mm apart. Calculate the number of elementary charges on the drop.

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**Q, 5. **Give an account of Bohr’s theory of H-atom. What is Bohr’s radius. Draw the energy level diagram of H-atom after calculating the value of En.

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**Q. 6.** Establish Einstein’s photo-electric equation by explaining the quantum postulates involved therein. How dies it explain the laws of photoelectric emission ?

An X-ray diffraction of a crystal gave the closest line at an angle of 6.5°. If the wave length of X-rays is 0.55 A, find the inter planar spacing for that reflection.

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**Q. 7. **Distinguish between nuclear fission and nuclear fusion. Give one example of each.

Calculate the energy released due to nuclear fission of a single U235 nucleus by a thermal neutron.

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**Q. 8. ** Write short notes on any two :

**(a) **Mosley’s law

**(b) **Normal Zeeman effect

**(c ) **Radioactive equilibria

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