Science (English Medium) Class 12 - CBSE Important Questions for Physics

Write the necessary conditions to obtain sustained interference fringes.

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?

Derive the expression of Brewster's law when unpolarised light passing from a rarer to a denser medium gets polarised on reflection at the inteface.

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.

Two polaroids P₁ and P₂ are placed with their pass axes perpendicular to each other. Unpolarised light of intensity I₀ is incident on P₁. A third polaroid P₃ is kept in between P₁ and P₂ such that its pass axis makes an angle of 60° with that of P₁. Determine the intensity of light transmitted through P₁, P₂ and P₃.

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?

The equivalent wavelength of a moving electron has the same value as that of a photon of energy 6 × 10^–17 J. Calculate the momentum of the electron.

What is mass defect?

Obtain the relation between the decay constant and half life of a radioactive sample.

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.

Write any two characteristic features of nuclear forces?

For a CE-transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100, find the input signal voltage and base current if the base resistance is 1 kΩ.

Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.

Draw the circuit diagram of a half wave rectifier and explain its working.

Describe briefly, with the help of a diagram, the role of the two important processes involved in the formation of a p-n junction.

Draw the circuit diagram of a full wave rectifier.