Important Questions for CBSE 12 Board Examination (Physics)

Q.1) What is the direction of the force acting on a charge particle q, moving with a velocity v in a uniform magnetic field B ?

Answer: 1.PNG

Q.2) Name the part of the electromagnetic spectrum of wavelength 10- 2 m and mention its one application.

Answer: 2.PNG

Q.3) An electron and alpha particle have the same de-Broglie wavelength associated with them. How are their kinetic energies related to each other ?

Answer: 3.PNG

Q.4) A glass lens of refractive index 1×5 is placed in a through of liquid. What must be the refractive index of the liquid in order to make the lens disappear ?

Answer: 4.PNG

Q.5) A 500 mC charge is at the centre of a square of side 10 cm. Find the work done in moving a charge of 10 mC between two diagonally opposite points on the square.


Q.6) State the reason, why heavy water is generally used as a moderator in a nuclear reactor.

Answer: The basic principle of mechanics is that momentum transfer is maximum when the mass of colliding particle and target particle are equal. Heavy water has negligible absorption cross-section for neutrons and its mass is small; so heavy water molecules do not absorb fast neutrons; but simply slow them.

Q.7) How does the fringe width of interference fringes change, when the whole apparatus of Young’s experiment is kept in a liquid of refractive index 1.3 ?



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