Science (English Medium) इयत्ता १२ - CBSE Important Questions for Physics

Define self-inductance of a coil.

State how a moving coil galvanometer can be converted into an ammeter.

How is current sensitivity increased?

In what way is Gauss's law in magnetism different from that used in electrostatics ? Explain briefly.

State Lenz's law. Illustrate, by giving an example, how this law helps in predicting the direction of the current in a loop in the presence of a changing magnetic flux.

In a given coil of self-inductance of 5 mH, current changes from 4 A to 1 A in 30 ms. Calculate the emf induced in the coil.

Derive the expression for the self-inductance of a long solenoid of cross sectional area A and length l, having n turns per unit length.

How are infrared waves produced?

How are X-rays produced?

Give any two uses of infrared waves.

In Young's double slit experiment, plot a graph showing the variation of fringe width versus the distance of the screen from the plane of the slits keeping other parameters same. What information can one obtain from the slope of the curve?

What is the effect on the fringe width if the distance between the slits is reduced keeping other parameters same?

In a double-slit experiment using the light of wavelength 600 nm, the angular width of the fringe formed on a distant screen is 0.1°. Find the spacing between the two slits.

Show that the angular width of the first diffraction fringe is half that of the central fringe.

A plane wavefront propagating in a medium of refractive index 'μ₁' is incident on a plane surface making the angle of incidence 'i' as shown in the figure. It enters into a medium of refractive index 'μ₂' (μ₂ > μ₁). Use Huygens' construction of secondary wavelets to trace the propagation of the refracted wavefront. Hence verify Snell's law of refraction.

Two monochromatic beams, one red and the other blue, have the same intensity. In which case (i) the number of photons per unit area per second is larger, (ii) the maximum kinetic energy of the photoelectrons is more? Justify your answer.

How does one explain, using de Broglie hypothesis, Bohr's second postulate of quantization of orbital angular momentum?

Draw a plot of potential energy of a pair of nucleons as a function of their separations. Mark the regions where the nuclear force is (i) attractive and (ii) repulsive.

Describe the following term briefly: 

minority carrier injection in forward biasing.

Describe the following term briefly:

breakdown voltage in reverse biasing