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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.

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40.
In photo-electric effect, what is meant by the terms :

(i) Work function of a metal

(ii) Stopping potential.

(i) Work function of a metal: The minimum energy, supplied to the electron so that it can just come out of a metal surface is called work function of a metal. It is denoted by w. Mathematically : W = R.v₀

(ii) Stopping Potential: The minimum potential (V₀), applied to the anode in a photo cell so that photo electric current becomes zero.

Mathematically,

$eV subscript straight o space equals space space 1 half space mu squared subscript max$