QUESTION PAPER
2022 BOARD EXAM
CBSE CLASS 12-PCM PHYSICS Board Paper 2022 — Set 4
2022
PHYSICS
CLASS 12-PCM
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 3 sections.
- Section A – questions number 1 to 1 are case based questions
- Section B – questions number 2 to 5 are very short answer
- Section C – questions number 6 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
(1) An object is placed at the point B as shown in the figure. The object distance (u) and the image distance (v) are related as
[1 Marks]
(2) A point object is placed in air at a distance 'R' in front of a convex spherical refracting surface of radius of curvature R. If the medium on the other side of the surface is glass, then the image is : (i) real and formed in glass. (ii) real and formed in air. (iii) virtual and formed in glass. (iv) virtual and formed in air.
(3) An object is kept at 2F in front of an equiconvex lens. The image formed is : (i) real and of the size of the object. (ii) virtual and of the size of the object. (iii) real and enlarged. (iv) virtual and diminished.
(4) A thin converging lens of focal length 10 cm and a thin diverging lens of focal length 20 cm are placed coaxially in contact. The power of the combination is : (i) -5 D (ii) + 5 D (iii) + 15 D (iv) -15 D
(5) An equiconcave lens of focal length 'f' is cut into two identical parts along the dotted line as shown in the figure. The focal length of each part will be : (i) f (ii) f/4 (iii) f/2 (iv) 2f
[1 Marks]
Section B
What is meant by energy band gap in a solid? Draw the energy band diagrams for a conductor, an insulator and a semiconductor.
Name the spectral series for a hydrogen atom which lies in the visible region. Find the ratio of the maximum to the minimum wavelengths of this series.
What are matter waves? A proton and an alpha particle are accelerated through the same potential difference. Find the ratio of the de Broglie wavelength associated with the proton to that with the alpha particle.
Section C
(a) Differentiate between nuclear fission and nuclear fusion.
(b) Deuterium undergoes fusion as per the reaction:
Find the duration for which an electric bulb of 500 W can be kept glowing by the fusion of 100 g of deuterium.
(a) The resistance of a p-n junction is low when it is forward biased and is high when it is reversed biased.
(b) Doping of intrinsic semiconductors is a necessity for making electronic devices.
(c) Photodiodes are operated in reverse bias.
(a) In Geiger-Marsden experiment, calculate the distance of closest approach for an alpha particle with energy 2.56 × 10⁻¹² J. Consider that the particle approaches gold nucleus (Z = 79) in head-on position.
(b) If the above experiment is repeated with a proton of the same energy, then what will be the value of the distance of closest approach?
Briefly explain how bright and dark fringes are formed on the screen in Young's double slit experiment. Hence, derive the expression for the fringe width.
a) (i) Draw a labelled ray diagram showing the formation of the image at infinity by an astronomical telescope.
(ii) A telescope consists of an objective of focal length 150 cm and an eyepiece of focal length 6.0 cm. If the final image is formed at infinity, then calculate:
(I) the length of the tube in this adjustment, and
(II) the magnification produced.
(a) Use Einstein photoelectric equation to depict the variation of the maximum kinetic energy (E_k) of electrons emitted with the frequency (v) of the incident radiation.
(b) A photosensitive surface is illuminated with a beam of (i) yellow light, and (ii) red light, both of the same intensity. In which case will
(I) photoelectrons have more E_k?
(II) more numbers of electrons be emitted?
Justify your answer in each case.
(i) Draw a labelled ray diagram showing the formation of the image at least distance of distinct vision by a compound microscope.
(ii) A small object is placed at a distance of 3.0 cm from a magnifier of focal length 4.0 cm.
Find:
(I) the position of the image formed, and
(II) the linear magnification produced.
(b) A plane wavefront is propagating from a rarer into a denser medium. Use Huygens principle to show the refracted wavefront and verify Snell's law.
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