Subject

Physics

Class

ICSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

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 Multiple Choice QuestionsShort 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 1.5x1011m?
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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.


Let S be a narrow slit luminated by monochromatic light, S1 and S2 be two parallel narrow slits very close to each other.

The light waves S reach S1 and S2 in some phase. According to Higgens principle S1 and S2 etc as new light sources from which secondary wavelet originate. These wavelet originate. These wavelets form interference fringes on screen.

Let a bright fringes be formed at P

Path difference. = (S2P - S1P)

ΔS2P - S1P = S2P - AP = S2A

 

In space increment straight S subscript 1 space straight S subscript 2 space straight A space sin space straight theta space equals space fraction numerator straight S subscript 2 straight A over denominator straight S subscript 1 space straight S subscript 2 end fraction

In space increment PCO space tan space straight theta space equals space OP over CO

sin space straight theta space rightwards arrow space space tan space straight theta space space rightwards arrow space straight theta

fraction numerator straight S subscript 2 straight A over denominator straight S subscript 1 space straight S subscript 2 end fraction space equals space OP over CO
fraction numerator
straight S subscript 2 straight A over denominator straight d end fraction space equals space straight x over straight p

straight S subscript 2 straight A space equals space xd over straight p
Position space of space bright space fringes comma space xd over straight D space equals space mλ
Dark space fringes comma space space xd over straight D space equals space left parenthesis 2 straight m space minus 1 right parenthesis straight lambda over 2
straight x space equals space left parenthesis straight m minus 1 half right parenthesis Dλ over straight d

Fringe space width comma space straight x subscript straight m space equals space mDλ over straight d
straight x subscript straight m plus 1 end subscript space equals space left parenthesis straight m plus 1 right parenthesis Dλ over straight d

Fringe space width comma space straight beta space equals space Dλ over straight d 

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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 (fr-fv) 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 : (fr-fv ) = 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.

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