Page 1 Sample Paper 09 CBSE Physics Class 12
Sample Paper 09
Class XII 2024-25
Physics
Time: 3 Hours Max. Marks: 70
General Instructions:
1. There are 33 questions in all. All questions are compulsory.
2. This question paper has five sections: Section A, Section B, Section C, Section D and Section E.
3. All the sections are compulsory.
4. Section A contains sixteen questions, twelve MCQ and four assertion reasoning based of 1 mark each,
Section B contains five questions of 2 marks each, Section C contains seven questions of 3 marks each,
Section D contains two case study based questions of 4 marks each and Section E contains three long
questions of 5 marks each.
5. There is no overall choice. However, an internal choice has been provided in one question in Section B,
one question in Section C, one question in each CBQ in Section D and all three questions in Section E.
You have to attempt only one of the choices in such questions
6. Use of calculators is not allowed.
7. You may use the following values of physical constants where ever necessary
i. c = 3 # 108 m/s
ii. me = 9.1 # 10−31 kg
iii. e = 1.6 # 10−19 C
iv. µ 0 = 4π # 10−7 TmA−1
v. h = 6.63 # 10−34 Js
vi. ε 0 = 8.854 # 10−12 C2 N−1 m−2
vii. Avogadro’s number = 6.023 # 1023 per gram mole
SECTION-A
1. The specific resistance of a conductor increases with-
(a) increase of temperature (b) increase of cross-sectional area
(c) decrease on length (d) decrease of cross-sectional area
2. The working of dynamo is based on the principle of
(a) heating effect of current (b) electromagnetic induction
(c) magnetic induction (d) electric induction
3. Comic rays are
(a) high energy radiations (b) low energy radiations
(c) ultra high energy radiations (d) very low energy radiations
4. An alternating current is given by: I = I1 cos ωt + I2 sin ωt . The root mean square current is given by
(I1 + I2) (I1 + I2) 2
(a) (b)
2 2
(c) I12 + I22 (d) I12 + I22
2 2
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Page 2 Sample Paper 09 CBSE Physics Class 12
5. Bright colours exhibited by spider’s web exposed to sun light are due to
(a) diffraction (b) polarisation
(c) interference (d) resolution
6. A plane mirror products a magnification of
(a) 0 (b) - 1
(c) + 1 (d) between 0 and + 1
7. Nuclear atom model is required to explain the results of
(a) Rydberg’s experiment (b) Rutherford’s experiment
(c) Thomson’s atom model (d) Bohr’s frequency condition
8. Permeability µ of a ferromagnetic substance
(a) µ >> 1 (b) µ = 1
(c) µ < 1 (d) µ = 0
9. If a current i ampere flows in a long straight thin walled tube, then magnetic induction at any point inside
the tube is
(a) zero (b) infinite
2i Tesla µ 0 2i
(c) (d) $ Tesla
r 4π r
10. Ampere-hour is unit of
(a) Power (b) Charge
(c) Energy (d) Potential difference
11. The electrostatic capacity of a capacitor depends upon its
(a) charge (b) potential
(c) resistance (d) both a and b
12. The de-Broglie wavelength λ depends upon mass m and energy E according to the relation represented as
(a) mE1/2 (b) m1/2 E
(c) m-1/2 E-1/2 (d) m-1/2 E1/2
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Page 3 Sample Paper 09 CBSE Physics Class 12
13. Assertion : The stars twinkle while the planets do not.
Reason : the stars are much bigger in size than the planets.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.
14. Assertion : Environmental damage has increased the amount of ozone in the atmosphere.
Reason : Increase of ozone increases the amount of ultraviolet radiation of earth.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.
15. Assertion (A) : Endoscopy involves use of optical fibres to study internal organs.
Reason (R) : Optical fibres are based on phenomena of total internal reflection.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.
16. Assertion : A white source of light during interference forms only white and black fringes.
Reason : Width of fringe is inversely proportional to the wavelength of the light used.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.
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SECTION-B
17. Write two uses of X -rays.
18. Plot a graph showing variation of current versus voltage for the material GaAs.
19. A uniform magnetic field gets modified as shown in the figure, when two specimens X and Y are placed
in it.
(a)
(b)
20. Why does thermionic emission take place from a metal surface only?
O
Write the relationship of de-Broglie wavelength λ associated with a particle of mass m in terms of its
kinetic energy E .
21. Draw equipotential surfaces due to a single point charge.
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SECTION-C
22. Write the expression for Bohr’s radius in hydrogen atom.
23. Explain, polarisation affords a convincing evidence of transverse nature of light.
24. Compare the properties of electric charge and mass which are not similar.
25. Define one tesla using the expression for the magnetic force acting on a particle of charge q moving with
velocity vv in a magnetic field Bv .
26. Distinguish between ‘Intrinsic’ and ‘extrinsic’ semiconductors?
27. Name and define the SI and CGS units of magnetic flux. Write the relation between them.
28. Answer the following questions
(i) Name the electromagnetic waves which are used for the treatment of certain forms of cancer. Write
their frequency range.
(ii) Thin ozone layer on top of stratosphere is crucial for human survival. Why ?
(iii) Why is the amount of the momentum transferred by the electromagnetic waves incident on the
surface so small ?
O
Answer the following questions :
(i) Show, by giving a simple example, how electromagnetic waves carry energy and momentum.
(ii) How are microwaves produced ? Why is it necessary in microwaves ovens to select the frequency of
microwaves to match the resonant frequency of water molecules ?
(iii) Write two important uses of infrared waves.
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SECTION-D
Case Study Based Questions.
Read the following paragraph and answer the questions that follow.
29. The electron mobility characterises how quickly an electron can move through a metal of semiconductor
when pulled by an electric field. There is an analogous quality for holes, called hole mobility. A block of
pure silicon at 300 K has a length of 10 cm and an area of 1.0 cm2. A battery of emf 2 V is connected across
it. The mobility of electron is 0.14 m2 V-1 s-1 and their number density is 1.5 # 1016 m-3 . The mobility of
holes is 0.05 m2 V-1 s-1 .
(i) The electron current is
(a) 6.72 # 10-4 A
(b) 6.72 # 10-5 A
(c) 6.72 # 10-6 A
(d) 6.72 # 10-7 A
(ii) The hole current is
(a) 2.0 # 10-7 A
(b) 2.2 # 10-7 A
(c) 2.4 # 10-7 A
(d) 2.6 # 10-7 A
(iii) The number density of donor atoms which are to be added up to pure silicon semiconductor to produce
an n-type semiconductor of conductivity 6.4 Ω−1 cm−1 is approximately (neglect the contribution of holes
to conductivity)
(a) 3 # 1022 m-3
(b) 3 # 1023 m-3
(c) 3 # 1024 m-3
(d) 3 # 1021 m-3
(iv) When the given silicon semiconductor is doped with indium, the hole concentration increases to
4.5 # 1023 m-3 . The electron concentration in doped silicon is
(a) 3 # 109 m-3
(b) 4 # 109 m-3
(c) 5 # 109 m-3
(d) 6 # 109 m-3
O
Pick out the statement which is not correct.
(a) At a low temperature, the resistance of a semiconductor is very high.
(b) Movement of holes is restricted to the valence band only.
(c) Width of the depletion region increases as the forward bias voltage increases in case of a p-n junction
diode.
(d) In a forward bias condition, the diode heavily conducts.
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30. The lens maker’s formula is a relation that connects focal length of a lens to radii of curvature of two
surfaces of the lens and refractive index of the material of the lens. It is 1f = (µ − 1) ` R1 − R1 j , where µ is
1 2
refractive index of lens material w.r.t. the medium in which lens is held. As µv > µr , therefore, fr > fv .
Mean focal length of lens for yellow colour is f = fr # fv .
(i) Focal length of a equiconvex lens of glass µ = 3
2 in air is 20 cm. The radius of curvature of each surface
is
(a) 10 cm (b) –10 cm
(c) 20 cm (d) –20 cm
(ii) A substance is behaving as convex lens in air and concave in water, then its refractive index is
(a) greater than air but less than water
(b) greater than both air and water
(c) smaller than air
(d) almost equal to water
(iii) For a thin lens with radii of curvatures R1 and R2 , refractive index n and focal length f, the factor
b R1 - R2 l is equal to
1 1
1 (b) f ^n - 1h
f ^n - 1h
(a)
^n - 1h n
f ^n - 1h
(c) (d)
f
(iv) A given convex lens of glass ^µ = 32 h can behave as concave when it is held in a medium of µ equal to
(a) 1 (b) 3/2
(c) 2/3 (d) 7/4
O
The radii of curvature of the surfaces of a double convex lens are 20 cm and 40 cm respectively, and its
focal length is 20 cm. What is the refractive index of the material of the lens?
(a) 5/2 (b) 4/3
(c) 5/3 (d) 4/5
SECTION-E
31. Define alternating current (AC), its peak value and its R.M.S. value. Derive relation between then after
evaluating the expression for R.M.S. value.
O
Using phaser diagram for a series LCR circuit connected to an AC source of voltage V = V0 sin ωt , derive
the relation for the current flowing in the circuit and the phase angle between the voltage across the
resistor and the net voltage in the circuit.
Draw a plot showing the variation of the current I as a function of angular frequency ‘ω ’ of the applied
AC source for the two cases of a series combination of
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(i) inductance L1 , Capacitance C1 and resistance R1 and
(ii) inductance L2 , Capacitance C2 and resistance R2 whereR2 2 R1
Write the relation between L1 , C1 and L2 , C2 at resonance. Which one of the two would be better suited
for fine tuning in a receiver set? Give reason.
32. Draw the graph showing the variation of binding energy per nucleon with the mass number for a large
number of nuclei 2 < A < 240 . What are the main inferences from the graph? How do you explain the
constancy of binding energy in the range 30 < A < 170 using the property that the nuclear force is short-
ranged? Explain with the help of this plot the release of energy in the processes of nuclear fission and
fusion.
O
Distinguish between nuclear fission and fusion. Show how in both these processes energy is released.
Calculate the energy release in MeV in the deuterium fusion reaction.
2 H + 3 H $ 4 He + n
1 1 2
Using the data
m b 2 H l = 2.014102 u
1
m b H l = 3.016049 u
3
1
m b He l = 4.002603 u
4
2
mn = 1.008665 u
1u = 931.5 MeV
c2
33. What are ohmic and non-ohmic conductors/resistors? State the conditions under which Ohm’s law is not
obeyed. Give one example of each type.
O
When 5 V potential difference is applied across a wire of length 0.1 m, the drift speed of electron is
2.5 # 10-4 m/s. If the electron density in the wire is 8 # 1028 m-3 , calculate the resistivity of the material
of wire.
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