Physics · 2022 · Set 55/4/1

CBSE Class 12 Physics 2022 — Set 55/4/1

CBSE Class XII Board 2022 · Set 55/4/1

Real board examination

Sets

About the 2022 exam: 2022 was CBSE's special COVID year: the board exam was split into two terms instead of one 70-mark paper. Term 1 (Dec 2021) was multiple-choice only; Term 2 (2022 — the papers shown here) was a shorter subjective paper of just 12 questions for 35 marks. So the smaller size IS the real exam that year, not missing content — 3 complete series (55/1/1, 55/2/1, 55/4/1) of 12 questions each. Some topics examined then have since been removed from the syllabus — badged and filterable above.

This paper has 2 questions on a topic removed in CBSE’s 2023-24 syllabus update (each marked Not in syllabus). It’s kept for historical accuracy — the exam really asked it that year — but isn’t in the current syllabus and doesn’t count toward a concept’s importance. Switch to to focus on what’s still examinable.

About this paper

The real Class-12 board examination held in 2022. Every question below is solved the concept-first way. Sample papers are labelled honestly — never shown as a past exam.

Total marks: 35
Questions: 12
Duration: 120 min
Sections: 3

The marks / questions / duration above are the official exam pattern. We currently have 12 of this paper’s questions (100% of the full paper), with 12 fully solved. Questions we couldn’t yet extract or verify are held — never shown as complete.

Sections & marks

Section	Type	Questions	Marks each	Total
ASection A	Short answer	3	2	6
BSection B	Short answer	8	3	24
CSection C	Case-based	1	5	5
Total		12		35

The question paper

The questions we hold for this paper, laid out by section. Solutions are on the Answers tab.

Board Examination

Physics

CBSE Class XII Board 2022 · Set 55/4/1

Series/Set: 55/4/1Roll No. ________

Time Allowed: 2 hoursMaximum Marks: 35

General Instructions

This question paper contains 12 questions divided into 3 sections — A, B, C.
Section A comprises 3 questions of 2 marks each (Short answer).
Section B comprises 8 questions of 3 marks each (Short answer).
Section C comprises 1 question of 5 marks each (Case-based).

Above is the official exam pattern. The questions printed below are those we currently hold for this paper.

Section A

Short answer · 2 marks each · 3 of 3 shown

Q1.

What is meant by energy band gap in a solid ? Draw the energy band diagrams for a conductor, an insulator and a semiconductor.

[2]

Q2.

(a) 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.

(OR)

(b) 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.

[2]

Q3.

Name the device which converts electrical energy into light energy. Write three advantages of the device.

⚠ This question is not in the current syllabus — Semiconductor Electronics (LED) (removed 2023-24)

[2]

Section B

Short answer · 3 marks each · 8 of 8 shown

Q1.

(a) Differentiate between nuclear fission and nuclear fusion.

(b) Deuterium undergoes fusion as per the reaction : ${}_{1}^{2}\mathrm{H} + {}_{1}^{2}\mathrm{H} \rightarrow {}_{2}^{3}\mathrm{He} + {}_{0}^{1}\mathrm{n} + 3\cdot27\ \mathrm{MeV}$ Find the duration for which an electric bulb of 500 W can be kept glowing by the fusion of 100 g of deuterium.

[3]

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Q2.

Answer the following, giving reason : (a) The resistance of a p-n junction is low when it is forward biased and is high when it is reverse biased. (b) Doping of intrinsic semiconductors is a necessity for making electronic devices. (c) Photodiodes are operated in reverse bias.

⚠ This question is not in the current syllabus — special-purpose p-n junction diodes (photodiode) (removed 2023-24)

[3]

Q3.

(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 ?

[3]

Q4.

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.

[3]

Q5.

(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. OR (b) (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.

[3]

Q6.

(a) Use Einstein's photoelectric equation to depict the variation of the maximum kinetic energy (Ek) of electrons emitted, with the frequency (nu) 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 Ek ? (II) more numbers of electrons be emitted ? Justify your answer in each case.

[3]

Q7.

A ray of light is incident on a prism at an angle of 45^° and passes symmetrically as shown in the figure. Calculate : (a) the angle of minimum deviation, (b) the refractive index of the material of the prism, and (c) the angle of refraction at the point P.

[3]

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Q8.

(a) Identify electromagnetic waves which : (i) are used in radar system. (ii) affect a photographic plate. (iii) are used in surgery. Write their frequency range. OR (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.

[3]

Section C

Case-based · 5 marks each · 1 of 1 shown

Q1.

Two transparent media of refractive indices n₁ and n₂ are separated by a spherical transparent surface. The rays of light incident on the surface get refracted into the medium on the other side. The laws of refraction are valid at each point of the spherical surface. A lens is a transparent optical medium bounded by two surfaces, at least one of which should be spherical. The focal length of a lens is determined by the radii of curvature (R₁ and R₂) of its two surfaces and the refractive index (n) of the medium of the lens with respect to the surrounding medium. Depending on R₁ and R₂, a lens behaves as a diverging or a converging lens. The ability of a lens to diverge or converge a beam of light incident on it defines its power. (a) 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 (i) (1)/(v)-(1)/(u)=((n₂-n₁)/(n₁))(1)/(R) (ii) (1)/(v)-(1)/(u)=((n₁-n₂)/(n₂))(1)/(R) (iii) (n₂)/(v)-(n₁)/(u)=((n₂-n₁))/(R) (iv) (n₁)/(v)-(n₂)/(u)=((n₁-n₂))/(R) (b) 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. (c) 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. (d) 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 (e) 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)/(4) (ii) (f)/(2) (iii) f (iv) 2f

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