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ISC Class 12 Physics Solved Question Paper 2013

Short Answer Type

31. (i) In an electromagnetic wave, how are electric vector E, magnetic vector B and velocity of propagation of the wave (c) oriented?

ii) How long would gamma radiation take to travel from sun to earth, a distance of 1.5x10^11m?

i) The relation is given by,

$straight E over straight B space equals space c$
ii) Speed of light, v = 3 x10⁸ m/s

Distance, d = 1.5 x 10¹¹ m

Time taken, t = $straight d over straight v space equals space fraction numerator 1.5 space straight x space 10 to the power of 11 over denominator 3 space straight x 10 to the power of 8 end fraction space equals space 0.5 space straight x space 10 squared space sec$

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32.

With the help of a labelled diagram, show that fringe separation β in Young’s double slit experiment is given by:

$straight beta space equals space λD over straight d$
where the terms have their usual meaning.

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33.

(i) What is the difference between polarised light unpolarised light based on the direction of electric vector E?

(ii) What will be the effect on the width of the central bright fringe in the diffraction pattern of a single slit if :

(1) Monochromatic light of smaller wavelength is used.

(2) Slit is made narrower.

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34.

At what angle, a ray of light should be incident on the first face AB of a regular glass prism ABC so that the emergent ray grazes the adjacent face AC? See Figure 7 below. (Refractive Index of glass = 1.6)

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35. A convex lens ‘L’ and a plane mirror ‘M’ are arranged as shown in Figure 8 below. Position of object pin ‘O’ is adjusted in such a way that the inverted image ‘I’ formed by the lens mirror combination, coincides with the object pin ‘s. Explain how and when this happens.

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36. Starting with an expression for refraction at a single spherical surface obtain an expression for lens maker’s formula.

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37. Show that the axial chromatic aberration (f_r-f_v) for a convex lens is equal to the product of its mean focal length (f) and dispersive power (ω ) of its material i.e. Prove : (f_r-f_v ) = ω f.

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38.

Draw a labelled diagram of an image formed by a compound microscope, with the image at least distance of distinct vision. Write any one expression for its magnifying power.

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39. What is meant by long-sightedness? How can this defect be corrected?

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40.

(i) What is meant by ‘Quantization of charge?

(ii) In Thomson’s experiment, prove that the ratio of charge to the mass (e/m) of an electron is given by :

$straight e over straight m space equals space fraction numerator 1 over denominator 2 V end fraction E squared over B squared$
where the terms have their usual meaning.