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ISC Class 12 Physics Solved Question Paper 2008

Short Answer Type

31. Draw a labelled diagram of Michelson’s method to determine the speed of light in air.

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32. What is the essential difference between polarised light and unpolarized light ? Find Brewster’s angle for water having refractive index n = 1.33.

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33.

When two thin lenses of focal lengths f₁ and f₂ are kept in contact, prove that their combined focal length 'f' is given by

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34. Draw a labelled Ray diagram of an image of a distant object formed by a refracting astronomical telescope in normal adjustment. Write (do not derive) an expression for its magnifying power.

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35. In a compound microscope consisting of two convex lenses of focal lengths 1.5 cm and 10 cm, the object is 2 cm from the objective and the final image is formed at the least distance of distinct vision (C = 25 cm). Find the distance of separation of the two lenses.

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36. A parallel beam of monochromatic light of wavelength 500 nm is incident normally on a rectangular slit. The angular width of the central bright fringe of Fraunhofer diffraction is found to be 60°. Find the width of the slit in metre.

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37.

An electron beam passes through crossed electric and magnetic fields of 3.4 x 10⁴ Vm^-1 and 2 x 10^-3 Wb mr^-2 respectively. If the path of the beam remains undeviated, calculate the speed of the electrons.

If the electric field is removed, what will be the radius of the circular path described by the electrons ?

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38.

Draw the energy level diagram of a hydrogen atom; and draw arrows to show transitions responsible for:

(i) Absorption lines of Lyman series.

(ii) Emission lines of Balmer series.

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39. Explain in brief the Compton Effect.

Comption Effect :

A. H. Comption observed that when a beam of monochromatic radiation of high frequency is allowed to fall on a substance of low atomic number like carbon, then the scattered radiation has to components.

(i) One component having the same frequency or wavelength as that of incident radiation.

(ii) The other component having lower frequency and longer wavelength.

The high frequency radiation in this scattering can be X-rays,γ-rays, etc. The scattered radiation having lower frequencies are called modified radiations and those having same frequency are called unmodified radiations. This phenomenon is called Comption effect or Comption scattering.

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