Revision Work Sheet MCQs

Class XII Physics

1. A The nature of parallel and anti-parallel currents are
(a) parallel currents repel and anti parallel currents attract.
(b) Parallel currents attract and anti parallel cur-rents repel.
(c) Both currents attract. ’
(d) both currents repel.
2. For a total internal reflection, which of the following is correct?
(a) Light travels from rarer to denser medium. (b) Light travels from denser to rarer medium.
(c) Light travels in air only. (d) Light travels in water only.
3. The locus of all particles in a medium, vibrating in the same phase is called
(a) wavelet (b) fringe (c) wave front (d) None of these
4. According to Coulomb's law, which is the correct relation for the following figure?

(i) q1 q2 > 0 (ii) q1 q2 < 0

(iii) q1 q2 = 0 (iv) 1 > q1/q2 > 0
5. The diffraction effect can be observed in
(A) Sound waves only (B) light waves only
(C) Ultrasonic waves only (D) sound waves as well as light waves
6. Correct match of column I with column II
C-l (waves) C-ll (Production)
(1) Infra-red P . Rapid vibration of electrons in aerials
(2) Radio waves Q . Electrons in atoms emit light when they
move from higher to lower energy level.
(3) Light R . Klystron valve
(4) Microwave S . Vibration of atoms and molecules
(A) 1-P, 2-R, 3-S, 4-Q (B) 1-S, 2-P, 3-O, 4-R
(C) 1-Q, 2-P, 3-S, 4-R (D) 1-S. 2-R, 3-P, 4-Q
7. A point object is placed at the centre of a glass sphere of radius 6 cm and refractive index 1.5. The distance of
virtual image from the surface of the sphere is
(A) 2 cm (B) 4 cm (C) 6 cm (D) 12 cm
8. The number of electrons made available for conduction by dopant atoms depends strongly upon
(A) Doping level (B) increase in ambient temperature
(C) Energy gap (D) options (A) and (B) both
9. The radius (rn) of n orbit in Bohr model of hydrogen atom varies with n as
th

(A) rn ∝ n (B) rn ∝ 1/n (C) rn ∝ n2 (D) rn ∝ 1/n2

10. A conducting wire connects two charged conducting spheres of radii r1 and r2 such that they attain equilibrium
with respect to each other. The distance of separation between the two spheres is very large as compared to either
of their radii. The ratio of the magnitudes of the electric fields at the surfaces of the spheres of radii r1 and r2 is
(A) �1/�2 (B) �2/�1 (C) (r2)2 /(r1)2 (D) (r1)2 /(r2)2
11. The magnitude of the electric field due to a point charge object at a distance of 4.0 m is 9N/C. From the same
charged object the electric field of magnitude, 16 N/C will be at a distance of
(A) 1m (B) 2 m (C) 3m (D) 6m
12. If the ammeter in the given circuit shown in the diagram reads 2 A, the resistance R is

(A) 1Ω (B) 2Ω (C) 3Ω (D) 4Ω

13. The constant k in Coulombs law depends on:

(i) Nature of medium (iii) Intensity of charge

 (ii) System of units (iv) Both (i) and (ii)

14. The ratio of magnitude of electrostatic force and gravitational force for an electron and a proton is :
6.6 x 1039 (ii) 2.4 x 10 39 (iii) 6.6 x 1029 (iv) 2.4 x 1039
15. Two point charges placed in a medium of dielectric constant 5 are at a distance r between them, experience an
electrostatic force ‘F’. The electrostatic force between them in vacuum at the same distance r will be-
(i) 5F (ii) F (iii) F/2 (iv) F/5
16. Electric field required to keep a water drop of mass m just to suspended when charged with 1 electron is:
(i) Mg (ii) mg/e (iii) emg (iv) em/g
17. An electric dipole placed in a non – uniform electric field can experience:
(i) Force (ii) Torque (iii) Both (i) & (ii) (iv) None of the above
18. Electromagnetic waves in laboratory are produced by
(a) JJ Thomson (b) Biot- Savarts (c) Hertz (d) Marconi
19. A Night vision camera uses
(a) X – rays (b) Infrared rays (c) Gamma rays (d) UV rays
20. If the frequency of oscillating particle is n then the frequency of oscillation of its energy is
(a) n (b) 2n (c)n/2 (d) 4n
21. An equiconvex lens of focal length 15 cm is cut into two halves .Find the focal length of each part?
(a) -30cm (b) -20cm (c) 30cm (d) -15cm
22. How does the focal length of a convex lens changes if mono chromatic red light is used instead of violet light?
(a) Focal length is increased when red light is used
(b) Focal length is decreased when red light is used
(c) Focal length is remained same when red light is used
(d) Not depends on color of light.
23. A glass lens is immersed in water. What will be the effect on the power of lens?
(a) increase (b) decrease (c) constant (d) not depends
24. How does the magnifying power of a telescope change on increasing the linear diameter of its objective?
(a) Power increases on increases diameter (b) Power decreases on decreases diameter
c) Power remains constant on increases diameter (d) Power doesn’t depends on diameter
25. In an experiment to measure the wavelength of light using a double slit, it is found that the fringes are too close
together to easily count them. To spread out the fringe pattern, one could:
A. decrease the slit separation B. increase the slit separation
C. increase the width of each slit D. decrease the width of each slit
26. No fringes are seen in a single-slit diffraction pattern if:
A. the screen is far away B. the wavelength is less than the slit width
C. the wavelength is greater than the slit width D. the wavelength is less than the distance to the screen
27. Which waves are suitable for radar system used in air craft navigation?
(a) Radio waves (b) Microwaves (c) Infrared waves (d) Visible rays.
28. When a highly coherent beam of light is directed against a very fine wire, the shadow formed behind it is not
just that of a single wire but rather looks like the shadow of several parallel wires. The explanation of this
involves:
A. refraction B. diffraction C. reflection D. the Doppler effect
29. A Monochromatic light is normally incident on a diffraction grating that is 1 cm wide and has 10, 000 slits. The
first order line is deviated at a 30◦ angle. What is the wavelength, in nm, of the incident light?
A. 300 B. 400 C. 500 D. 600
30. In photoelectric effect, electrons are ejected from metals if the incident light has a certain minimum
(a) Wavelength (b)Frequency (c)Amplitude (d)Angle if incidence
31. A Packet of energy are called
 (a)electron (b) quanta (c)frequency (d)neutron
32. Energy associated with each photon
(a)hc (b) mc (c) hv (d)hk
33. The radii of two nuclei with mass number 1 and 27 respectively are in the ratio of
(a)3: 1 (b)2: 1 (c) 1: 3 (d) 2:1
34. The cause of the potential barrier in a p-n junction diode is
(a) depletion of positive charges near the junction
(b) concentration of positive charges near the junction
(c) depletion of negative charges near the junction
(d) concentration of positive and negative charges near the junction
35. Electromagnetic waves travelling in a medium having relative permeability μr = 1.3 and relative permittivity Er
= 2.14. The speed of electromagnetic waves in medium must be
(a) 1.8 × 108 ms-1 (b) 1.8 × 104ms1 (c) 1.8 × 106ms1 (d) 1.8 × 10² ms-1
36. An electric dipole is
(i) a pair of electric charges of equal magnitude q but positive sign, separated by a distance d
(ii) a pair of electric charges of equal magnitude q but opposite sign, separated by a distance
(iii) a pair of electric charges of equal magnitude q but negative sign, separated by a distance d
(iv) a pair of electric charges of equal magnitude q separated by a distance d
37. The nucleus of helium atom contains two protons that are separated by a distance 3 x 10-15m. The magnitude
of the electrostatic force that each proton exerts on the other is:
(i) 20.6 N (ii) 25.6 N (iii) 15.6 N (iv) 12.6 N
In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct
answer out of the following choices. [1 x 4 = 4]
a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
c) Assertion is correct statement but reason is wrong statement.
d) Assertion is wrong statement but reason is correct statement.