CBSE Class 12 Physics Question Paper 2007 (Delhi)

CBSE CLASS XII Questions

• 1.

  An astronomical telescope consists of two converging lenses. One of them of large aperture and large focal length is called objective lens and the other one, of smaller focal length and smaller aperture is called the eyepiece. It is used to see distant objects which are not seen clearly with naked eyes. The image formed by the objective lens acts as an object for the eyepiece and the final image produced by the eyepiece is magnified.
  

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• 2.

  Read the following paragraph and answer the questions that follow.
  A p-type or n-type semiconductor can be converted into a p-n junction by doping it with suitable impurity. The motion of majority charge carriers causes diffusion current across the junction while the barrier electric field causes motion of minority carriers for drift current. In case of unbiased diode, the diffusion and drift currents are equal. This equilibrium is disturbed by the biasing batteries. Diodes, therefore, allow currents in one direction. This property of diode is used in making rectifiers.
  

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• 3.

  With the help of a labelled diagram, explain the principle, construction and working of an a.c. generator.
  

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• 4.

  A student sets up the circuit as shown in the figure to find the value of unknown resistance X and records a set of readings of the voltmeter and the ammeter by using the rheostat.
  

  

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• 5.

  Write two advantages of reflecting telescope over refracting telescope.
  

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• 6.

  Consider the nuclear reaction \( X \to Y + Z \). Let \( M_x \), \( M_y \), and \( M_z \) be the masses of the three nuclei X, Y, and Z respectively. Then which of the following relations hold true?

  • \( (M_x - M_z)<M_y \)
    
  • \( (M_x - M_y)<M_z \)
    
  • \( M_x>(M_y + M_z) \)
    
  • \( M_x<(M_y + M_z) \)
    
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