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ISC Class 12 Physics Solved Question Paper 2006

Short Answer Type

31. Name the essential parts of a spectrometer.

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32.

(i) Draw a ray diagram to show how the image of a distant object is formed by a refracting astronomical telescope when in normal use.

(ii) State one advantage of a reflecting astronomical telescope over a refracting astronomical telescope.

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33. The refractive indices of a material for red, violet and yellow colour lights are 1.52. 1.62 and 1.59 respectively. Calculate the dispersive power of the material. If the mean deviation is 40°, what will be the angular dispersion produced by a prism of this material ?

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34. What is the cause of spherical aberration in lenses? State a method to minimise this defect.

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35. In a Cathode ray tube, an electron passes through a field, where the electric field E and the magnetic field B are uniform and mutually perpendicular. Derive an expression for the velocity at which the electron reaches the screen undeflected.

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36.

(i) What is meant by the term activity of a radioactive substance.

(ii) A radioactive sample has a half life of 1.4 x 10¹⁶ seconds and a mass number of 238. Calculate the number of disintegration/s of 1g of this sample.

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37.

Which of the radiations, α-rays, β-rays, or γ-rays are :

(i) easily absorbed by matter ?

(ii) similar to X-rays ?

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38. From Bohr's energy quantization formula, determine the largest wavelength in the Balmer series of hydrogen atom spectrum.

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39. Draw a labelled diagram of a nuclear reactor, stating the function of each part.

An atomic reactor is a furnace in which energy is produced by the nuclear fission process.

The essential component of a reactor are as follows :

(i) Fuel: Uranium enriched with U²³⁵ or Pu²³⁹.

(ii) Moderator: The function of the moderator is to slow down the neutrons. Heavy water. Graphite or beryllium oxide is used as moderator.

(iii) Control rods : To control the chain reaction from becoming violent, rods of neutron absorbing materials like boron steel or cadmium can be inserted into the reactor core.

(iv) Coolant: The fusion product carry large kinetic energy with them. This is manifested as rise in temperature. Heat energy so produced is utilised in vapouring water or liquid sodium.

(v) Shielding: The entire reactor is provided with a thick concrete wall so that radiations emitted during the operation of a reactor may not be hazardous to a person in immediate vicinity.

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