CBSE Class 12 Physics 2022 question paper (55/3)

Maximum marks 35 · Time 2 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

2 marks each

Q.12 marks $What is meant by doping of an intrinsic semiconductor ? Name the two types of atoms used for doping of Ge/Si.$
Q.2 (a)2 marks $A_1$
OR
Q.2 (b)2 marks $(i) Name the factors on which photoelectric emission from a surface depends. (ii) Define the term 'threshold frequency' for a photosensitive material.$
Q.32 marks $Explain the formation of the barrier potential in a p-n junction.$

Section B

3 marks each

Q.43 marks $n^{th}$
Q.53 marks $Briefly explain how emf is generated in a solar cell. Draw its I-V characteristics.$
Q.63 marks $(Z = 82)$
Q.73 marks $In a diffraction pattern due to a single slit, how will the angular width of central maximum change, if (i) Orange light is used in place of green light, (ii) the screen is moved closer to the slit, (iii) the slit width is decreased ? Justify your answer in each case.$
Q.8 (a)3 marks $41.1^\circ$
OR
Q.8 (b)3 marks $(a) An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is (i) negative and (ii) positive. (b) A point object is placed at O in front of a glass sphere as shown in figure. Show the formation of image by the sphere.$
Q.93 marks $An electron is accelerated from rest through a potential difference of 100 V. Find : (i) the wavelength associated with (ii) the momentum of and (iii) the velocity required by, the electron.$
Q.103 marks $In a Young's double slit experiment using light of wavelength 600 nm, the slit separation is 0.8 mm and the screen is kept 1.6 m from the plane of the slits. Calculate : (i) the fringe width (ii) the distance of (a) third minimum and (b) fifth maximum, from the central maximum.$
Q.11 (a)3 marks $\lambda_1$
OR
Q.11 (b)3 marks $(i) State two conditions for two light sources to be coherent. (ii) Give two points of difference between an interference pattern due to a double – slit and a diffraction pattern due to a single slit.$

Section C

1 mark each

A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both the lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye piece, in turn produces the final magnified image.
Q.12 (I)1 mark $In a compound microscope the images formed by the objective and the eye-piece are respectively$
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Q.12 (II)1 mark $The magnification due to a compound microscope does not depend upon$
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Q.12 (III)1 mark $Which of the following is not correct in the context of a compound microscope ?$
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Q.12 (IV)1 mark $A compound microscope consists of an objective of 10X and an eye-piece of 20X. The magnification due to the microscope would be$
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Q.12 (V)1 mark $The focal lengths of objective and eye-piece of a compound microscope are 1.2 cm and 3.0 cm respectively. The object is placed at a distance of 1.25 cm from the objective. If the final image is formed at infinity, the magnifying power of the microscope would be$
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Section A

2 marks each

Q.12 marks $Explain the formation of the barrier potential in a p-n junction.$
Q.22 marks $(a) Draw the circuit diagram of an illuminated photodiode and its I-V charcteristics. (b) How can a photodiode be used to measure the light intensity ?$
Q.3 (a)2 marks $A_1$
OR
Q.3 (b)2 marks $(i) Name the factors on which photoelectric emission from a surface depends. (ii) Define the term 'threshold frequency' for a photosensitive material.$

Section B

3 marks each

Q.43 marks $6.5 \times 10^{-19}$
Q.53 marks $Monochromatic light of wavelength 600 nm is incident from air on a water surface. The refractive index of water is 1.33. Find the (i) wavelength, (ii) frequency and (iii) speed, of reflected and refracted light.$
Q.6 (a)3 marks $\lambda_1$
OR
Q.6 (b)3 marks $(i) State two conditions for two light sources to be coherent. (ii) Give two points of difference between an interference pattern due to a double – slit and a diffraction pattern due to a single slit.$
Q.73 marks $n^{th}$
Q.83 marks $Draw the energy band diagrams for conductors, semiconductors and insulators. Which band determines the electrical conductivity of a solid ? How is the electrical conductivity of a semiconductor affected with rise in its temperature ? Explain.$
Q.93 marks $(Z = 82)$
Q.103 marks $How is the spacing between fringes in a double slit experiment affected if : (i) the slits separation is increased, (ii) the colour of light used is changed from red to blue, (iii) the whole apparatus is submerged in a oil of refractive index 1.2 ? Justify your anwer in each case.$
Q.11 (a)3 marks $41.1^\circ$
OR
Q.11 (b)3 marks $(a) An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is (i) negative and (ii) positive. (b) A point object is placed at O in front of a glass sphere as shown in figure. Show the formation of image by the sphere.$

Section C

1 mark each

A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both the lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye piece, in turn produces the final magnified image.
Q.12 (I)1 mark $In a compound microscope the images formed by the objective and the eye-piece are respectively$
Tap an option to check your answer.
Q.12 (II)1 mark $The magnification due to a compound microscope does not depend upon$
Tap an option to check your answer.
Q.12 (III)1 mark $Which of the following is not correct in the context of a compound microscope ?$
Tap an option to check your answer.
Q.12 (IV)1 mark $A compound microscope consists of an objective of 10X and an eye-piece of 20X. The magnification due to the microscope would be$
Tap an option to check your answer.
Q.12 (V)1 mark $The focal lengths of objective and eye-piece of a compound microscope are 1.2 cm and 3.0 cm respectively. The object is placed at a distance of 1.25 cm from the objective. If the final image is formed at infinity, the magnifying power of the microscope would be$
Tap an option to check your answer.

Section A

2 marks each

Q.1 (a)2 marks $A_1$
OR
Q.1 (b)2 marks $(i) Name the factors on which photoelectric emission from a surface depends. (ii) Define the term 'threshold frequency' for a photosensitive material.$
Q.22 marks $Explain the formation of the barrier potential in a p-n junction.$
Q.32 marks $Name the extrinsic semiconductors formed when a pure germanium is doped with (i) a trivalent and (ii) pentavalent impurity. Draw the energy band diagrams of extrinsic semiconductors so formed.$

Section B

3 marks each

Q.4 (a)3 marks $41.1^\circ$
OR
Q.4 (b)3 marks $(a) An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is (i) negative and (ii) positive. (b) A point object is placed at O in front of a glass sphere as shown in figure. Show the formation of image by the sphere.$
Q.53 marks $6.4 \times 10^{14}$
Q.63 marks $A beam of light consisting of two wavelengths 600 nm and 500 nm is used in a Young's double slit experiment. The slit separation is 1.0 mm and the screen is kept 0.60 m away from the plane of the slits. Calculate : (i) the distance of the second bright fringe from the central maximum for wavelength 500 nm, and (ii) the least distance from the central maximum where the bright fringes due to both the wavelengths coincide.$
Q.7 (a)3 marks $\lambda_1$
OR
Q.7 (b)3 marks $(i) State two conditions for two light sources to be coherent. (ii) Give two points of difference between an interference pattern due to a double – slit and a diffraction pattern due to a single slit.$
Q.83 marks $In a diffraction pattern due to a single slit, how will the angular width of central maximum change, if (i) Orange light is used in place of green light, (ii) the screen is moved closer to the slit, (iii) the slit width is decreased ? Justify your answer in each case.$
Q.93 marks $Briefly explain how emf is generated in a solar cell. Draw its I-V characteristics.$
Q.103 marks $(a) James Chadwick, in 1932, studied the emission of neutral radiations when Beryllium nuclei were bombarded with alpha particles. He concluded that emitted radiations were neutrons and not photons. Explain. (b) Two nuclei may have the same radius, even though they contain different number of protons and neutrons. Explain.$
Q.113 marks $-1.51$

Section C

1 mark each

A compound microscope consists of two converging lenses. One of them, of smaller aperture and smaller focal length is called objective and the other of slightly larger aperture and slightly larger focal length is called eye-piece. Both the lenses are fitted in a tube with an arrangement to vary the distance between them. A tiny object is placed in front of the objective at a distance slightly greater than its focal length. The objective produces the image of the object which acts as an object for the eye-piece. The eye piece, in turn produces the final magnified image.
Q.12 (I)1 mark $In a compound microscope the images formed by the objective and the eye-piece are respectively$
Tap an option to check your answer.
Q.12 (II)1 mark $The magnification due to a compound microscope does not depend upon$
Tap an option to check your answer.
Q.12 (III)1 mark $Which of the following is not correct in the context of a compound microscope ?$
Tap an option to check your answer.
Q.12 (IV)1 mark $A compound microscope consists of an objective of 10X and an eye-piece of 20X. The magnification due to the microscope would be$
Tap an option to check your answer.
Q.12 (V)1 mark $The focal lengths of objective and eye-piece of a compound microscope are 1.2 cm and 3.0 cm respectively. The object is placed at a distance of 1.25 cm from the objective. If the final image is formed at infinity, the magnifying power of the microscope would be$
Tap an option to check your answer.