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ISC Class 12 Physics Solved Question Paper 2012

Short Answer Type

31. In Young’s double slit experiment using monochromatic light of wave-length 600 nm, interference pattern was obtained on a screen kept l-5m away from the plane of the two slits. Calculate the distance between the two slits, if fringe separation/fringe width was found to be 1-0 mm.

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32. Draw a labelled graph to show variation in intensity of diffracted light with angular position, in a single slit diffraction experiment.

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33. You are provided with a narrow and parallel beam of light. State how you will determine experimentally, whether it is a beam of ordinary (unpolarized) light, partially polarised light or completely polarised light.

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34. For any prism, show that refractive index of its material is given by:

straight n space or space straight mu space equals space fraction numerator sin space open parentheses begin display style fraction numerator straight A space plus straight delta subscript straight m over denominator 2 end fraction end style close parentheses over denominator sin space open parentheses begin display style straight A over 2 end style close parentheses end fraction

where the terms have their usual meaning.

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35. Figure 6 below shows a parallel beam of monochromatic light incident on a convex spherical surface, radius of curvature R = 30 cm, which separates glass (refractive index = 1.6) from air. Find the position of the image formed due to refraction of light at this single spherical surface.

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36.

(i) What is meant by:

(A) Spherical aberration?

(B) Chromatic aberration?

(ii) How can spherical aberration be reduced/minimized? Suggest any one method.

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37. A compound microscope consists of an objective of focal length 2 cm and an eye piece of focal length 5 cm. When an object is kept 2.4 cm from the objective, final image formed is virtual and 25 cm from the eye piece. Determine magnifying power of this compound microscope in this set up i.e. in normal use.

Given,

f₀ = focal length of the objective = 2 cm

f_e = focal length of the eye pieces = 5 cm

M_e = Magnification of the eye pieces

M_o = Magnification of the objective

M_e = 1 + $straight D over straight f subscript straight o$ = $1 space plus space 25 over 5 space equals space 6$
For the objective,

u = -2.4 cm, v = ? and f_o = 2 cm

$1 over straight v minus fraction numerator 1 over denominator negative 2.4 end fraction space equals space 1 half space space space space space space space space space space space space space space space space space space space space space equals space 1 half space minus space fraction numerator 1 over denominator 2.4 end fraction space space space space space space space space space space space space space space space space space space space space space equals space 12 over 24 minus 10 over 24 space space space space space space space space space space space space space space space space space space space space space equals space 2 over 24 space equals space 12 space c m M subscript o space space equals space v over u equals fraction numerator 12 over denominator 2.4 end fraction space equals space 5$

M = magnifying power of the compound microscope.

M = M₀ x M_e = 5 x 6 = 30, is the required magnification.

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38.

(i) Define Resolving Power of a simple astronomical telescope.

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

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39.

ndeviated through a uniform electric field $straight E with rightwards harpoon with barb upwards on top$ for intensity 5 x 10⁴ Vm^-1 and a uniform magnetic field $straight B with rightwards harpoon with barb upwards on top$ .

(i) Find the magnitude of magnetic flux density B of the magnetic field.

(ii) What is the direction of $straight B with rightwards harpoon with barb upwards on top space comma space if space space straight v with rightwards harpoon with barb upwards on top$ is towards right and $straight E with rightwards harpoon with barb upwards on top$ is vertically downwards in the plane of this paper?