QUESTION PAPER
2022 BOARD EXAM
CBSE CLASS 12-PCB PHYSICS Board Paper 2022 — Set 2
2022
PHYSICS
CLASS 12-PCB
CBSE EXAMINATION PAPER-2022
PHYSICS
(Solved)
General Instructions :
Read the following instructions carefully and follow them :
- This question paper contains 14 questions. All questions are compulsory.
- This question paper is divided into 2 sections.
- Section A – questions number 1 to 4 are very short answer
- Section B – questions number 5 to 14 are short answer
- There is no overall choice given in the question paper. However, an internal choice has been provided in few questions.
- Use of calculator is NOT allowed.
Section A
(a) (i) Define the terms : ' impact parameter' and 'distance of closest approach' for an α -particle in Geiger-Marsden scattering experiment.
(ii) What will be the value of the impact parameter for scattering angle (I) θ= 0 degree and (II) θ= 180 degree?
(b) Photoelectric emission occurs when a surface is irradiated with the radiation of frequency (i) v1, and (ii) v2. The maximum kinetic energy of the electrons emitted in the two cases are K and 2K respectively. Obtain the expression for the threshold frequency for the surface.
Section B
(a) (i) Depict a plane electromagnetic wave propagating along the x-axis. Write the expressions for its oscillating electric and magnetic fields.
(ii) Write three characteristics of electromagnetic waves.
(a) State the conditions for total internal reflection to take place.
(b) A tank is filled with a transparent liquid to height 'H'. A coin suspended by a thread in the liquid is gradually lowered till it touches the bottom. The apparent depth is determined corresponding to different positions of the coin.
(i) Plot a graph showing variation of the apparent depth with the real depth of the coin.
(ii) What is the physical significance of the slope of the graph ?
(a) Draw a labelled ray diagram showing the formation of an image by an astronomical refracting telescope in normal adjustment. Hence, obtain the expression for its magnifying power.
A converging lens made of glass ( μ= 1·5) has its spherical faces of radii of curvature 10 cm and 20 cm. Find its focal length
(a) in air, and
(b) when it is immersed in a liquid of refractive index 1·25.
The energy of a hydrogen atom in the first excited state is -3.4 eV. Find :
(a) the radius of this orbit. (Take Bohr radius = 0·53 Å)
(b) the angular momentum of the electron in the orbit.
(c) the kinetic and potential energy of the electron in the orbit.
(a) Depict the variation of the potential energy of a pair of nucleons with the separation between them.
(b) Imagine the fission of a 56 /26Fe into two equal fragments of 28 /13 Al nucleus. Is the fission energetically possible ? Justify your answer
by working out Q value of the process.
Given : m 56 /26 Fe = 55·93494 u, m 28/ 13 Al = 27·98191 u.
Find the ratio of the de Broglie wavelengths associated with an alpha particle and a proton, if both
(a) have the same speeds,
(b) have the same kinetic energy,
(c) are accelerated through the same potential difference.
With the help of a circuit diagram, explain the working of a p-n junction diode as a full-wave rectifier. Also draw its input and output waveforms.
(b) Name the electromagnetic waves which are produced by the following :
(i) Radioactive decays of nucleus
(ii) Welding arcs
(iii) Hot bodies
Write one use each of these waves.
(b) A plane wavefront of light of wavelength 'λ' is incident normally on a narrow slit of width 'a' and a diffraction pattern is observed on a screen at a distance 'D' from the slit.
(i) Depict the intensity distribution in the pattern observed.
(ii) Obtain the expression for the first maximum from the central maximum.
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