Subject

Physics

Class

CBSE 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

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11. How are side bands produced?


When the audio frequency modulating signal wave is superimposed on a high-frequency wave called carrier wave, the modulation process produces frequencies that are the sum and difference of carrier and modulating frequencies. These frequencies are side bands.

Lower side band frequency =  

Upper side band frequency = 

where

 is the carrier wave frequency and
 is the modulating/audio signal frequency.

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12.

A proton and an α-particle have the same de-Broglie wavelength. Determine the ratio of (i) their accelerating potentials (ii) their speeds.

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13.

Show that the radius of the orbit in hydrogen atom varies as , where n is the principal quantum number of the atom. 

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14. Distinguish between intrinsic and extrinsic semiconductors? 
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15.

Use the mirror equation to show that an object placed between f and 2f of a concave mirror produces a real image beyond 2f?

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16. Find an expression for intensity of transmitted light when a polaroid sheet is rotated between two crossed polaroids. In which position of the polaroid sheet will the transmitted intensity be maximum?
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17.

(i) A giant refracting telescope has an objective lens of focal length 15 m. If an eye piece of focal length 1.0 cm is used, what is the angular magnification of the telescope?

(ii) If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens ? The diameter of the moon is 3.48 × 106  m and the radius of lunar orbit is 3.8 × 108 m.
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18.

Write Einstein’s photoelectric equation and mention which important features in photoelectric effect can be explained with the help of this equation. The maximum kinetic energy of the photoelectrons gets doubled when the wavelength of light incident on the surface changes from  straight lambda subscript 1 to straight lambda subscript 2 . Derive the expressions for the threshold wavelength  straight lambda subscript straight o and work function for the metal surface. 

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19.

In the study of Geiger-Marsdon experiment on scattering of α particles by a thin foil of gold, draw the trajectory of -particles in the coulomb field of target nucleus. Explain briefly how one gets the information on the size of the nucleus from this study. From the relation R = Ro A1/3 where Ro is constant and A is the mass number of the nucleus, show that nuclear matter density is independent of A. 

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20.

Distinguish between nuclear fission and fusion. Show how in both these processes energy is released.

Calculate the energy release in MeV in the deuterium-tritium fusion reaction: 

Error converting from MathML to accessible text.
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