EXPECTED QUESTION IN PHYSICS CBSE – BOARD EXAMINATION 2011

EXPECTED QUESTION IN PHYSICS  CBSE – BOARD EXAMINATION 2011

1. State Gauss‘s Theorem. Using the Theorem, derive an expression for the electric field due to a thin infinitely long straight line of charge.

2. State the underlying principle of a transformer. Draw a lebelled diagram of a step down transformer. Mention two sources of energy losses in a transformer.

3. Prove law of refraction by using Huygens principle with neat labeled ray diagram.

4. Derive lens makers formula with neat labeled diagram. Also write the assumptions to be followed.

5. The wavelength λ of a photon and the de-Broglie wavelength of an electron have same value. Show that the energy of the photon is   times the kinetic energy of the electron, where m,c and h have their usual meanings.

(or)

Monochromatic light of frequency 6.0 ×10¹⁴ Hz is produced by a laser. The power emitted is 2.0 ×10^–3 W. (a) what is the energy of a photon in the light beam? (b) How many photons per second, on an average, are emitted by the source?

6. State the basic postulates of Bohr’s theory of atomic spectra. Hence obtain an expression for radius of Bohr’s orbit of a hydrogen atom.

7. Draw the circuit diagram to show the use of a transistor as an oscillator and explain its working.
8. State Ampere’s circuital law and write its mathematical form. Using the law derive an expression for the magnetic field along the axis of an air cored solenoid. Sketch the magnetic lines for a finite solenoid. What is the nature of the magnetic field inside the solenoid?

(or)

     Draw a neat and labeled diagram of a cyclotron. State the underlying principle

     and explain how a positively charged particle gets accelerated in this machine.

     Show mathematically that the cyclotron frequency does not depend upon the

     speed of the particle.

9. Draw a ray of light deviated by a prism. Find the expression for total deviations suffered by the light ray. Draw a graph showing the variation of the angle of deviation with the angle of incidence. Also derive the expression for the refractive index of the material of the prism.

(or)

     (i)Draw a course of rays through a compound microscope. Arrive an

      expression for its magnifying power.                                                                 3M

     (ii)A compound microscope with an objective of focal length f_o = 1.0 cm, and

     an eyepiece with focal length f_e = 2.0 cm, and a tube length of 20 cm.

     Calculate the magnification of the microscope for normal adjustment.

“BEST OF LUCK”