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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.

Here,

i = Angle of incidence

e= Angle of emergence

A = refracting angle

r + r’ = Angle of a refraction

δ = deviation

i + e = A + δ ---(i)

A = r₁+ r₂---(ii)

Above relation connecting i. c., A + δ are shown above.

Under minimum deviation i = e, r_t = r₂ = r

From Eq. (i), we have

2 i = A + δ min

$i space equals space fraction numerator straight A space plus space straight delta subscript min over denominator 2 end fraction space space space space space space space space space space space space space space space space space space space space space space space space space space space space... space left parenthesis i v right parenthesis F r o m space e q n. left parenthesis i i right parenthesis A space equals 2 r r space equals A over 2 space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space... space left parenthesis v right parenthesis mu space equals space fraction numerator s i n space i over denominator s i n space r end fraction space space space space space space space space space space space space space space space space space space space space space space space space space space space... space left parenthesis v i right parenthesis F r o m space E q. space left parenthesis i v right parenthesis comma space left parenthesis v right parenthesis space a n d space left parenthesis v i right parenthesis space w e space g e t mu space equals space fraction numerator S i n space open parentheses begin display style fraction numerator A space plus space delta subscript m i n end subscript over denominator 2 end fraction end style close parentheses over denominator s i n space open parentheses begin display style A over 2 end style close parentheses end fraction$

Hence proved.

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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.

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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?