Class 12 Physics Question Paper 2nd
CLASS - XII
General Instructions
1. All the questions are compulsory there are 33 questions in all. Total 10
pages are there.
2. The question paper has five sections: Section A, Section B, Section C, Section
D and Section E.
3. Section A contains sixteen questions, twelve MCQ and four assertion
reasoning based of 1 mark each, Section B contains five questions of two
marks each, Section C contains seven questions of three marks each, Section
D contains two case study-based questions of four marks each and Section
E contains three long answer questions of five marks each.
4. There is no overall choice. However, an internal choice has been provided in
Two question in Section B, one question in Section C and all three questions
in Section E. You have to attempt only one of the choices in such questions.
5. Use of calculators is not allowed.
You may use the following values of physical constants wherever necessary:
c = 3 x 108 m/s
h = 6.63 x 10-34 Js
e = 1.6 x 10-19 C
µ₀ = 4π × 10-7 Tm A-¹
ε₀ = 8.854 × 10-12 C²N-1 m-2
1/4πε₀ = 9 x 109 N m²C-2
Mass of electron (mₑ) = 9.1 x 10-31 kg
Mass o f neutron = 1.675 x 10-27 kg
Mass of proton = 1.673 x 10-27 kg
Avogadro's number = 6.023 x 10²³ per gram mole
Boltzmann constant = 1.38 x 10-23 JK-1
SECTION - A
1. If a light ray of wavelength λ is incident on a prism of refractive
index µ and small angle A, then the ray will be deviated with an
angle proportional to:
(a) refractive index of prism material.
(b) wavelength of light.
(c) frequency of light.
(d) angle of incidence.
2. The graph shows the variation of resistance of a metal wire as a
function of its diameter with lengths l₁ and l₂ then,
(a) Resistance of a wire is indirectly proportional to its length.
(b) For the same diameter, the wire with a greater length will have
a lower resistance.
(c) We have sufficient information to conclude that l₁> l₂
(d) All above statements are correct.
3. The magnetic field at a point 15 cm away from a straight wire carrying
6 A current will be:
(a) 4 x 10-6 T (b) 8 x 10-6 T
(c) 12 x 10-6 T (d) 2 x 10-6 T
4. Prism of angle 2º deviates an incident ray through an angle of 1º, then
the refractive index of the prism's material will be:
(a) 1.5 (b) 3 (c) 2.5 (d) 1
5. Which of the following statement is true?
(a) Electrostatic force is a conservative force.
(b) Potential at a point is the work done per unit charge in bringing a
charge from any point to infinity.
(c) Electrostatic force is non-conservative.
(d) Potential is the product of charge and work.
6. A dipole is placed in a uniform electric field directed from west to east.
If the position of dipole is along the electric field then:
(a) the torque acting on the dipole is negative.
(b) no torque is acting on the dipole.
(c) the torque acting on the dipole is positive.
(d) the torque acting on the dipole is infinite.
7. If an EM wave has B, Bo sin (100t-20πx) then we can deduce that:
(a) It is propagating along-ve x-axis with electric field oscillation in-ve
y-axis.
(b) It is propagating along +ve x-axis with electric field oscillations
along-ve y-axis.
(c) It is propagating along-ve x-axis with electric field oscillation along
+ve y-axis.
(d) It is propagating along +ve x-axis with electric field oscillation
along +ve y-axis.
8. The phase relationship between current and voltage in a pure resistive
circuit is best represented by:
9. In a Wheatstone bridge, three resistances P, Q and R are connected in
the three arms and the fourth arm is formed by two resistances S₁ and
S₂ connected as show figure.
Which of the following statement is NOT true for this circuit?
(I) No current will flow in the galvanometer arm of the Wheatstone
bridge when PS₁ S₂ = RQ (S₁ + S₂)
(II) The bridge will be balanced when P/Q = R/S where S is
(S₁+S₂) / S₁S₂
(III) If resistances S₁ and S₂ are connected in series instead of parallel,
then Q should be decreased to maintain the balanced state.
(a) only (I) (b) both (II) and (III)
(c) only (III) (d) both (I) and (II)
10. Three point charges q, -2q and -Q are placed at corners of an
equilateral triangle of a side 'a' as shown in figure. The relation
between Q and q for which potential at the centre of the square is
zero, is:
(a) Q = q (b) Q = -q
(c) Q = -2q (d) Q = 2q
11. Consider the following statements regarding Young's Double Slit
Experiment (YDSE):
1. If the wavelength of light used is increased, the fringe width will
increase.
2. If the whole YDSE apparatus is immersed in water (µ = 1.5), the
fringe width will decrease by 1.5 times.
3. If the distance between the slits and the screen (D) is decreased,
the fringe width will decrease.
4. If one of the slits is blocked with an opaque object, the fringe
pattern will disappear.
Choose the correct option:
(a) All statements are correct.
(b) Only statements 1, 2, and 4 are correct.
(c) Only statements 1 and 3 are correct.
(d) Only statements 2 and 3 are correct.
12. Two identical objects are moving with constant speed towards two
optical devices X and Y with following results.
Devices Device type Motion of object Motion of light
X Mirror Uniform motion Non- uniform motion away from X
Y Lens Uniform motion Non- uniform motion away from Y
Identify X and Y.
(a) X: Concave mirror, Y: Concave lens
(b) X: Concave mirror, Y: Convex lens
(c) X: Convex mirror, Y: Concave lens
(d) X: Convex mirror, Y: Convex lens
For Questions 13 to 16, two statements are given one labelled Assertion (A) and other labelled Reason (R). Select the correct answer to these questions from the options as given below.
(a) Both Assertion and Reason are true and Reason is the correct
explanation of Assertion.
(b) Both Assertion and Reason are true but Reason is not the correct
explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Both Assertion and Reason are false.
13. Assertion (A): For larger magnification, a simple microscope of
magnification 10 can be used.
Reason (R): The second lens is used in simple microscope for
enhancing the effect of other.
14. Assertion (A): When a rectangular coil is placed in magnetic field, it
starts rotating.
Reason (R): The force on two perpendicular arms of a rectangular
coil placed in a magnetic field is equal and opposite.
15. Assertion (A): When AC current is flowing through LCR circuit and
L = C, current and emf are in phase with each other.
Reason (R): Impedance of the circuit becomes equal to the R.
16. Assertion (A): When white light passes through a glass prism, the
deviation produced is minimum for the red color.
Reason (R): The angle of deviation depends on the refractive
index of the prism for the color of light, and red light
has the lowest refractive index in glass.
SECTION - B
17. Show that the Gauss's law helds true for magnetic field of a point
dipole moment M at the origin for the surface which is a sphere of
radius r?
18. Two wires of aluminium and copper of radius 0.12 cm are connected
in series carrying current of 20 A.
(A) What will be the current density in aluminium wire?
(B) Calculate the drift velocity of electrons in copper wire if number
density of electrons is 8.4 x 10²/m³.
OR
Rahul is trying to fix LED lights for diwali. He has only one wire and
the cell he was using last year is being replaced by a cell with twice
the emf. He thought of increasing the resistivity of his wire to
compensate for that. To increase resistivity of a conductor what
factors should Rahul change and how?
19. Draw the figures of p-n junction diode showing the difference in the
widths of the depletion layer in forward and reversed biasing.
20. The graph below shows the variation of the stopping potential (V) vs
the frequency (v) of incident light for two different materials 'X' and
'Y'.
From the given graph, identify:
(A) Which material has the higher work function?
(B) Which material exhibits the photoelectric effect at a lower
frequency?
OR
Plot a graph showing variation of maximum kinetic energy of
photoelectrons with frequency for two different value of intensities
I, and I₂ of incident radiation.
21. A full-wave rectifier is supplied with 220 V, 50 Hz AC. The
transformer has a turns ratio of 10:1, and the diodes are ideal.
Calculate:
(A) the average DC output voltage.
(B) the DC output current, if the load resistance R₁=100 Ω.
(C) the output frequency of the rectifier. (Take n = 3.14)
SECTION - C
22. If R is a high value resistance then will the galvanometer behave as a
voltmeter? If yes then derive the expression for required value of R
in terms of required range of voltmeter.
OR
(A) Draw a neat, labeled diagram showing two identical short bar
magnets, each having a magnetic moment of 24 Am², placed
perpendicular to each other as described: one along the X-axis
and the other along the Y-axis. The center-to-center distance
between their poles is such that point P lies at equal distances of
5 cm from the center of each magnet.
(B) Calculate the resultant magnetic field at point P (midpoint
between the two magnets).
23. Neha uses a portable electric lamp to light up her keyboard when working on her computer at night. The lamp consists of two small
bulbs each of resistance 2 Ω connected in series and is powered by a 20 V battery.
(A) How much current is drawn by the portable lamp?
(B) Each of the two bulbs in the portable lamp is rated for continuous
use of 10 hours only before they burn out. If the battery can
supply a total energy of 4000 kJ, which of the two occurs first: the
lamp burns out or the battery drains out? Show the working.
24. Mass number of a nucleus of an atom is A, by neglecting the mass of
the orbital electrons. Find the nuclear density of the nucleus ?
25. An optical instrument is designed with following specifications.
Identify the instrument and calculate its angular magnification if
image is formed at infinity.
26. For a p-n junction diode, following data is obtained:
Biasing V I
Forward 2 V
2.4 V 60 mA
80 mA
Reverse 0 V
-2 V 0 µA
-0.25 µA
Find the forward and reverse biased resistance of the given diode.
27. Draw labeled diagram of an AC circuit consisting of an inductor (L),
a capacitor (C), and three resistors R1, R2, R3 arranged such that R1
is in series with a parallel combination of R2 and R3. This entire
combination is in series with L and C. Derive an expression for
impedance of this circuit.
28. (A) In a nuclear reactor, 1 g of U-235 undergoes complete fission. If
each fission releases 200 MeV of energy, calculate the total
energy produced. How long could this energy power a 100 W
bulb.
(B) Calculate the energy released in fusion reaction:
2H1 + 2H1 → 3He2 + n
Given, BE of 2He1 = 2.23 MeV and of ₃He = 7.73 MeV.
SECTION - D
29. When two tuning forks are struck simultaneously, they produce
sound waves almost in the same phase. Their phase difference varies
slowly with time. Such variations can be detected easily by human
ear. The phase difference between two independent light bulb
changes by 10 per second. Therefore, we can observe interference of
sound using our senses but we cannot observe the interference
pattern of light.
(A) Which of the given graph shows correct relation between wave
number and angular frequency?
(B) If a thin film of mica is added as shown in the figure in Young's
double experiment then the fringes:
(a) shift towards P (b) shift towards Y
(c) become narrower (d) disappear entirely
(C) If the ratio of two intensities of two waves is 9:1, then the ratio of
amplitude of two waves:
(a) 9:1 (b) 1:9 (c) 3:1 (d) 1:3
(D) The figure shows two waves travelling in a medium with same
amplitude A but different frequencies. The resultant amplitude
of these waves at point P is:
(a) A (b) 2 A (c) A/2 (d) zero
30. De-Broglie hypothesis show that wave particle duality was not only
a behaviour of light but was a fundamental principle exhibited by
both radiation and matter. It is possible to use wave equation to
describe material behaviour as long as one properly applies the
de-Broglie wavelength. Though the broglie hypothesis predicts
wavelength of matter of any size, there are realistic limits only when
it's useful. A cricket ball shot towards the boundary has de-Broglie
wavelength smaller than the diameter of a proton by about 20 orders
of magnitude.
(A) Two cars, A and B, are in motion. Car A has speed v and de-Broglie
wavelength λ. Car B moves with twice the speed of car A and has
double the kinetic energy. Determine 2 the de-Broglie
wavelength of car B in terms of λ.
(B) A cricket ball of mass 60 g is moving with velocity 11 m/s.
Calculate its de-Broglie wavelength. How does de-Broglie
wavelength change if we double the velocity of ball? 1
(C) Draw a graph showing the variation of de Broglie wavelength of
a particle of charge q and mass m with accelerating potential.
SECTION - E
31. With the help of a diagram, explain the construction and working of
an astronomical telescope when it forms final image at the least
distance of distinct vision and at infinity.
OR
(A) With the wavefront diagram, explain what should be the
approximate size of the aperture to observe the diffraction of
light.
(B) Distinguish between diffraction and interference.
32. (A) Using phasor diagram, derive an expression for the average value
of power over a cycle when an AC voltage is applied to a resistor.
(B) If peak voltages are given to be 200 V and resistor has a what will
be the average power dissipated?
OR
(A) If a source of emf is connected to an inductor L and current starts
inducing an opposite emf in the inductor, derive an expression
for energy spent by the source to send current through the circuit
against the induced emf?
(B) What will be the energy stored in an inductor of 20 mH if current
grows from zero to 5 A?
33. (A) Demonstrate that the heat produced is minimized when a
current is split between two resistors in accordance with
Kirchoff's laws.
(B) Plot a graph showing variation of current in a conductor with
drift velocity of electrons.
OR
(A) Define emf of a cell? On what factors does it depend?
(B) Calculate the current flowing through resistor R if internal
resistances of cell 9 V and 3 V is 2 Ω and 4 Ω respectively.
(C) A bulb is connected across diagonal of a square arrangement of
four resistors such that it does not glow when the arrangement
is connected to a battery. Identify the circuit. What will be the
current in bulb if the P, Q, R and S are 2 Ω, 4 Ω, 3 Ω and 6 Ω
respectively.
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