CBSE Class 12 Physics 2022 question paper (55/5)

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 $With the help of a circuit diagram, explain briefly how a p-n junction diode works as a half-wave rectifier.$
Q.2 (a)2 marks $\alpha$
OR
Q.2 (b)2 marks $Why it is the frequency and not the intensity of light source that determines whether emission of photoelectrons will occur or not ? Explain.$
Q.32 marks $Why a photo-diode is operated in reverse bias whereas current in the forward bias is much larger than that in the reverse bias ? Explain. Mention its two uses.$

Section B

3 marks each

Q.43 marks $\theta$
Q.53 marks $(i) Draw V-I characteristics of a p-n Junction diode. (ii) Differentiate between the threshold voltage and the breakdown voltage for a diode. (iii) Write the property of a junction diode which makes it suitable for rectification of ac voltages.$
Q.63 marks ${}^{238}_{92}\mathrm{U}$
Q.73 marks $How can you differentiate whether a pattern is produced by a single slit or double slits ? Derive the expression for the angular position of (i) bright and (ii) dark fringes produced in a single slit diffraction.$
Q.8 (a)3 marks $(i) Define SI unit of power of a lens. (ii) A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of the convex surface is 25 cm. (ii.i) Calculate the focal length of the lens. (ii.ii) If an object is placed 50 cm in front of the lens, find the nature and position of the image formed.$
OR
Q.8 (b)3 marks $A slit of width 0.6 mm is illuminated by a beam of light consisting of two wavelengths 600 nm and 480 nm. The diffraction pattern is observed on a screen 1.0 m from the slit. Find : (i) The distance of the second bright fringe from the central maximum pertaining to light of 600 nm. (ii) The least distance from the central maximum at which bright fringes due to both the wavelengths coincide.$
Q.93 marks $(a) Calculate the energy and momentum of a photon in a monochromatic beam of wavelength 331.5 nm. (b) How fast should a hydrogen atom travel in order to have the same momentum as that of the photon in part (a) ?$
Q.103 marks $\sqrt{2}$
Q.11 (a)3 marks $(i) Arrange the following electromagnetic radiation in the ascending order of their frequencies : X-rays, microwaves, gamma rays, radio waves (ii) Write two uses of any two of these radiation.$
OR
Q.11 (b)3 marks $With the help of a ray diagram explain the working of a reflecting telescope. Mention two advantages of a reflecting telescope over a refracting telescope.$

Section C

1 mark each

A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased farther the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light.
Q.12 (i)1 mark $18^\circ$
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Q.12 (ii)1 mark $\mu$
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Q.12 (iii)1 mark $For which of the following media, with respect to air, the value of critical angle is maximum ?$
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Q.12 (iv)1 mark $The critical angle for a pair of two media A and B of refractive indices 2.0 and 1.0 respectively is :$
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Q.12 (v)1 mark $30^\circ$
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Section A

2 marks each

Q.12 marks $\mathrm{C_1}$
Q.22 marks $Why a photo-diode is operated in reverse bias whereas current in the forward bias is much larger than that in the reverse bias ? Explain. Mention its two uses.$
Q.3 (a)2 marks $\alpha$
OR
Q.3 (b)2 marks $Why it is the frequency and not the intensity of light source that determines whether emission of photoelectrons will occur or not ? Explain.$

Section B

3 marks each

Q.43 marks $\mathrm{S_1}$
Q.53 marks $= 6.4 \times 10^{-27}$
Q.6 (a)3 marks $(i) Define SI unit of power of a lens. (ii) A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of the convex surface is 25 cm. (ii.i) Calculate the focal length of the lens. (ii.ii) If an object is placed 50 cm in front of the lens, find the nature and position of the image formed.$
OR
Q.6 (b)3 marks $A slit of width 0.6 mm is illuminated by a beam of light consisting of two wavelengths 600 nm and 480 nm. The diffraction pattern is observed on a screen 1.0 m from the slit. Find : (i) The distance of the second bright fringe from the central maximum pertaining to light of 600 nm. (ii) The least distance from the central maximum at which bright fringes due to both the wavelengths coincide.$
Q.7 (a)3 marks $(i) Arrange the following electromagnetic radiation in the ascending order of their frequencies : X-rays, microwaves, gamma rays, radio waves (ii) Write two uses of any two of these radiation.$
OR
Q.7 (b)3 marks $With the help of a ray diagram explain the working of a reflecting telescope. Mention two advantages of a reflecting telescope over a refracting telescope.$
Q.83 marks $\sqrt{2}$
Q.93 marks $n^{th}$
Q.103 marks $(i) Draw V-I characteristics of a p-n Junction diode. (ii) Differentiate between the threshold voltage and the breakdown voltage for a diode. (iii) Write the property of a junction diode which makes it suitable for rectification of ac voltages.$
Q.113 marks ${}^{238}_{92}\mathrm{U}$

Section C

1 mark each

A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased farther the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light.
Q.12 (i)1 mark $18^\circ$
Tap an option to check your answer.
Q.12 (ii)1 mark $\mu$
Tap an option to check your answer.
Q.12 (iii)1 mark $For which of the following media, with respect to air, the value of critical angle is maximum ?$
Tap an option to check your answer.
Q.12 (iv)1 mark $The critical angle for a pair of two media A and B of refractive indices 2.0 and 1.0 respectively is :$
Tap an option to check your answer.
Q.12 (v)1 mark $30^\circ$
Tap an option to check your answer.

Section A

2 marks each

Q.12 marks $Give two differences between a half wave rectifier and a full wave rectifier.$
Q.22 marks $Why a photo-diode is operated in reverse bias whereas current in the forward bias is much larger than that in the reverse bias ? Explain. Mention its two uses.$
Q.3 (a)2 marks $\alpha$
OR
Q.3 (b)2 marks $Why it is the frequency and not the intensity of light source that determines whether emission of photoelectrons will occur or not ? Explain.$

Section B

3 marks each

Q.4 (a)3 marks $(i) Define SI unit of power of a lens. (ii) A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of the convex surface is 25 cm. (ii.i) Calculate the focal length of the lens. (ii.ii) If an object is placed 50 cm in front of the lens, find the nature and position of the image formed.$
OR
Q.4 (b)3 marks $A slit of width 0.6 mm is illuminated by a beam of light consisting of two wavelengths 600 nm and 480 nm. The diffraction pattern is observed on a screen 1.0 m from the slit. Find : (i) The distance of the second bright fringe from the central maximum pertaining to light of 600 nm. (ii) The least distance from the central maximum at which bright fringes due to both the wavelengths coincide.$
Q.53 marks $An electron in a hydrogen atom makes transitions from orbits of higher energies to orbits of lower energies. (i) When will such transitions result in (a) Lyman (b) Balmer series ? (ii) Find the ratio of the longest wavelength in Lyman series to the shortest wavelength in Balmer series.$
Q.63 marks $With the help of a ray diagram, show how a compound microscope forms a magnified image of a tiny object, at least distance of distinct vision. Hence derive an expression for the magnification produced by it.$
Q.73 marks $6.06\times10^{-19}\mathrm{J}$
Q.83 marks ${}^{238}_{92}\mathrm{U}$
Q.9 (a)3 marks $(i) Arrange the following electromagnetic radiation in the ascending order of their frequencies : X-rays, microwaves, gamma rays, radio waves (ii) Write two uses of any two of these radiation.$
OR
Q.9 (b)3 marks $With the help of a ray diagram explain the working of a reflecting telescope. Mention two advantages of a reflecting telescope over a refracting telescope.$
Q.103 marks $\sqrt{2}$
Q.113 marks $(i) Draw V-I characteristics of a p-n Junction diode. (ii) Differentiate between the threshold voltage and the breakdown voltage for a diode. (iii) Write the property of a junction diode which makes it suitable for rectification of ac voltages.$

Section C

1 mark each

A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased farther the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light.
Q.12 (i)1 mark $18^\circ$
Tap an option to check your answer.
Q.12 (ii)1 mark $\mu$
Tap an option to check your answer.
Q.12 (iii)1 mark $For which of the following media, with respect to air, the value of critical angle is maximum ?$
Tap an option to check your answer.
Q.12 (iv)1 mark $The critical angle for a pair of two media A and B of refractive indices 2.0 and 1.0 respectively is :$
Tap an option to check your answer.
Q.12 (v)1 mark $30^\circ$
Tap an option to check your answer.