Class 12 Physics Ch-8 Electromagnetic Waves MCQs Exam 2027

Unit 1: Electrostatics

1. The value of $1/4\pi\epsilon_0$ is: [BSEB, 2021 (A)]

   (A) $9 \times 10^9 \, Nm^2C^{-2}$

   (B) $9 \times 10^{-9} \, Nm^2C^{-2}$

   (C) $9 \times 10^{12} \, Nm^2C^{-2}$

   (D) $9 \times 10^{-12} \, Nm^2C^{-2}$

2. Which of the following relations is correct? [BSEB, 2021 (A)]

   (A) $\vec{E} = \vec{F}/q$

   (B) $\vec{E} = q\vec{F}$

   (C) $\vec{E} = \vec{F}/q^2$

   (D) $\vec{E} = 1/4\pi\epsilon_0 \cdot q/F$

3. Electric potential is equal to: [BSEB, 2021 (A)]

   (A) $q/W$

   (B) $W/q$

   (C) $Wq$

   (D) $\sqrt{Wq}$

4. Dielectric constant of water is: [BSEB, 2021 (A)]

   (A) 80

   (B) 60

   (C) 1

   (D) 42.5

5. The value of $\epsilon_r$ in air is: [BSEB, 2021 (A)]

   (A) Zero

   (B) Infinity

   (C) 1

   (D) $9 \times 10^9$

6. SI unit of electric dipole moment is: [BSEB, 2021 (A)]

   (A) $C \cdot m$

   (B) $C/m$

   (C) $C \cdot m^2$

   (D) $C^2 \cdot m$

7. Relative permittivity ($\epsilon_r$) of a medium is: [BSEB, 2021 (A)]

   (A) $\epsilon/\epsilon_0$

   (B) $\epsilon \times \epsilon_0$

   (C) $\epsilon + \epsilon_0$

   (D) $\epsilon – \epsilon_0$

8. How many electrons are there in 1 Coulomb of charge? [BSEB, 2024 (A)]

   (A) $6.25 \times 10^{18}$

   (B) $1.6 \times 10^{-19}$

   (C) $6.25 \times 10^{19}$

   (D) $1.6 \times 10^{19}$

9. Surface density of charge is equal to: [BSEB, 2021 (A)]

   (A) Total charge $\times$ Total area

   (B) Total charge / Total area

   (C) Total charge / Total volume

   (D) Total charge $\times$ Total volume

10. The unit of capacitance of a capacitor is: [BSEB, 2020 (A)]

    (A) Volt

    (B) Newton

    (C) Farad

    (D) Ampere

11. Energy of a charged conductor is: [BSEB, 2021 (A)]

    (A) $E = CV^2$

    (B) $E = \frac{1}{2}CV^2$

    (C) $E = \frac{1}{3}CV^2$

    (D) $E = \frac{1}{4}CV^2$

12. Which of the following is correct for the capacitance of a parallel plate capacitor? [BSEB, 2021 (A)]

    (A) $\epsilon_0 A/d$

    (B) $\epsilon_0 d/A$

    (C) $d/\epsilon_0 A$

    (D) $A/\epsilon_0 d$

13. If $n$ capacitors of equal capacitance $C_1$ are connected in parallel, the equivalent capacitance will be: [BSEB, 2021 (A)]

    (A) $nC_1$

    (B) $C_1/n$

    (C) $n^2C_1$

    (D) $C_1/n^2$

14. The value of permittivity of free space ($\epsilon_0$) is: [BSEB, 2021 (A)]

    (A) $8.85 \times 10^{-12} \, Fm^{-1}$

    (B) $8.85 \times 10^{-13} \, Fm^{-1}$

    (C) $8.85 \times 10^{-14} \, Fm^{-1}$

    (D) $8.85 \times 10^{-11} \, Fm^{-1}$

15. Dimension of electric intensity is: [BSEB, 2024 (A)]

    (A) $[MLT^{-3}A^{-1}]$

    (B) $[MLT^{-2}A^{-1}]$

    (C) $[ML^2T^{-3}A^{-1}]$

    (D) $[MLT^{-3}A]$

Unit 2: Current Electricity

16. 16. Which of the following is correct for the resistivity of a material? [BSEB, 2021 (A)]

        (A) $\rho = RA/l$

        (B) $\rho = l/RA$

        (C) $\rho = Rl/A$

        (D) $\rho = RA \cdot l$

    17. Power of electric circuit is: [BSEB, 2021 (A)]

        (A) $V \cdot R$

        (B) $V^2 \cdot R$

        (C) $V^2/R$

        (D) $V^2 R \cdot I$

    18. Kilowatt-hour (kWh) is the unit of: [BSEB, 2020 (A)]

        (A) Power

        (B) Energy

        (C) Torque

        (D) Current

    19. The motion of electrons inside a conductor is: [BSEB, 2022 (A)]

        (A) Uniform

        (B) Accelerated

        (C) Drifting

        (D) Decelerated

    20. In the color code of carbon resistance, the value of yellow color is: [BSEB, 2021 (A)]

        (A) 1

        (B) 2

        (C) 3

        (D) 4

    21. Voltmeter measures: [BSEB, 2021 (A)]

        (A) Resistance

        (B) Potential difference

        (C) Current

        (D) Charge

    22. Resistance of an ideal ammeter is: [BSEB, 2021 (A)]

        (A) Zero

        (B) Very small

        (C) Very large

        (D) Infinity

    23. Which of the following is correct for current density? [BSEB, 2022 (A)]

        (A) $J = I \cdot A$

        (B) $J = I/A$

        (C) $J = A/I$

        (D) $J = I^2 \cdot A$

    24. Electromotive force (emf) of a cell is measured by: [BSEB, 2021 (A)]

        (A) Voltmeter

        (B) Ammeter

        (C) Galvanometer

        (D) Potentiometer

    25. SI unit of specific resistance is: [BSEB, 2023 (A)]

        (A) Ohm-meter ($\Omega m$)

        (B) Ohm/meter ($\Omega / m$)

        (C) Ampere-meter

        (D) Ohm-meter$^2$

    26. Wheatstone bridge is used to measure: [BSEB, 2024 (A)]

        (A) Only high resistance

        (B) Only low resistance

        (C) Both high and low resistance

        (D) Potential difference

27. If a copper wire is stretched to double its length, its resistance will become: [BSEB, 2026]

    (A) Two times

    (B) Four times

    (C) Half

    (D) Unchanged

28. The element used in electric heaters is: [BSEB, 2017 (A)]

    (A) Copper

    (B) Platinum

    (C) Tungsten

    (D) Nichrome

29. Ampere-hour is the unit of: [BSEB, 2022 (A)]

    (A) Power

    (B) Charge

    (C) Energy

    (D) Potential difference

30. Kirchhoff’s Point Rule follows: [BSEB, 2021 (A)]

    (A) Principle of conservation of energy

    (B) Principle of conservation of charge

    (C) Principle of conservation of momentum

    (D) Principle of conservation of mass

Unit 3: Magnetic Effects of Current & Magnetism

31. A moving charge produces: [BSEB, 2022 (A)]

    (A) Only electric field

    (B) Only magnetic field

    (C) Both electric and magnetic fields

    (D) None of these

32. Unit of magnetic flux is: [BSEB, 2021 (A)]

    (A) Weber ($Wb$)

    (B) Weber/meter$^2$

    (C) Tesla

    (D) Henry

33. $\vec{F} = q(\vec{v} \times \vec{B})$ is called: [BSEB, 2021 (A)]

    (A) Lorentz force

    (B) Coulomb force

    (C) Nuclear force

    (D) Gravitational force

34. Resistance of an ideal voltmeter is: [BSEB, 2021 (A)]

    (A) Zero

    (B) $100 \, \Omega$

    (C) $1000 \, \Omega$

    (D) Infinity

35. Tesla is the unit of: [BSEB, 2022 (A)]

    (A) Magnetic flux

    (B) Magnetic field

    (C) Magnetic induction

    (D) Electric field

36. Cyclotron is not suitable for accelerating which particle? [BSEB, 2026]

    (A) Proton

    (B) Neutron

    (C) Alpha-particle

    (D) Deuteron

37. Value of angle of dip at the magnetic poles of Earth is: [BSEB, 2021 (A)]

    (A) $0^\circ$

    (B) $45^\circ$

    (C) $90^\circ$

    (D) $180^\circ$

38. Nickel is: [BSEB, 2021 (A)]

    (A) Diamagnetic

    (B) Paramagnetic

    (C) Ferromagnetic

    (D) None of these

39. Relation between magnetic geometric length ($L_g$) and magnetic length ($L_m$) is: [BSEB, 2020 (A)]

    (A) $L_m = \frac{5}{6}L_g$

    (B) $L_m = \frac{6}{5}L_g$

    (C) $L_m = L_g$

    (D) $L_m = 2L_g$

40. Permeability ($\mu$) is equal to: [BSEB, 2021 (A)]

    (A) $B/H$

    (B) $H/B$

    (C) $B \cdot H$

    (D) $B + H$

41. Value of relative permeability ($\mu_r$) is: [BSEB, 2021 (A)]

    (A) $\mu/\mu_0$

    (B) $\mu_0/\mu$

    (C) $\mu \cdot \mu_0$

    (D) $\mu + \mu_0$

42. Dimension of magnetic induction is: [BSEB, 2024 (A)]

    (A) $[MT^{-2}A^{-1}]$

    (B) $[MLT^{-2}A^{-1}]$

    (C) $[MT^{-2}A]$

    (D) $[ML^2T^{-2}A^{-1}]$

43. Magnetic susceptibility ($\chi$) of a paramagnetic substance is: [BSEB, 2019 (A)]

    (A) Constant

    (B) Zero

    (C) Infinity

    (D) Depends on magnetic field

44. SI unit of pole strength is: [BSEB, 2021 (A)]

    (A) $N$

    (B) $N/A \cdot m$

    (C) $A \cdot m$

    (D) $T$

45. Value of magnetic susceptibility of vacuum is: [BSEB, 2021 (A)]

    (A) 0.5

    (B) Infinity

    (C) 1

    (D) Zero

Unit 4: EMI & Alternating Current

46. SI unit of self-inductance is: [BSEB, 2021 (A)]

    (A) Coulomb

    (B) Volt

    (C) Ohm

    (D) Henry

47. Lenz’s law is a consequence of the principle of conservation of: [BSEB, 2021 (A)]

    (A) Current

    (B) Momentum

    (C) Energy

    (D) Charge

48. Direction of induced emf is found by: [BSEB, 2024 (A)]

    (A) Lenz’s Law

    (B) Fleming’s Left Hand Rule

    (C) Fleming’s Right Hand Rule

    (D) Both (A) and (C)

49. Relation between root-mean-square value ($I_{rms}$) and peak value ($I_0$) of AC is: [BSEB, 2021 (A)]

    (A) $I_{rms} = 0.507 I_0$

    (B) $I_{rms} = 0.707 I_0$

    (C) $I_{rms} = 0.607 I_0$

    (D) $I_{rms} = 0.807 I_0$

50. In an AC circuit with angular frequency $\omega$, the inductive reactance ($X_L$) of an inductor of inductance $L$ is: [BSEB, 2021 (A)]

    (A) $\omega / L$

    (B) $\omega \cdot L$

    (C) $1 / \omega L$

    (D) $L / \omega$

51. Capacitive reactance ($X_C$) is: [BSEB, 2021 (A)]

    (A) $\omega C$

    (B) $C / \omega$

    (C) $\omega / C$

    (D) $1 / \omega C$

52. Which of the following is the correct relation for Power Factor? [BSEB, 2021 (A)]

    (A) $\text{Power Factor} = \text{True average power} / \text{Apparent average power}$

    (B) $\text{Power Factor} = \text{Apparent average power} / \text{True average power}$

    (C) $\text{Power Factor} = \text{True average power} \times \text{Apparent average power}$

    (D) None of these

53. Impedance ($Z$) of an $L-R$ circuit is: [BSEB, 2021 (A)]

    (A) $R + \omega L$

    (B) $\sqrt{R^2 + \omega^2 L^2}$

    (C) $\sqrt{R + \omega L}$

    (D) $R^2 + \omega^2 L^2$

54. Which of the following is correct for a transformer? [BSEB, 2021 (A)]

    (A) It converts DC into AC

    (B) It converts AC into DC

    (C) It is used to increase or decrease DC voltage

    (D) It is used to increase or decrease AC voltage

55. In a Step-up transformer, the relation between $N_2$ and $N_1$ is: [BSEB, 2021 (A)]

    (A) $N_2 > N_1$

    (B) $N_1 > N_2$

    (C) $N_1 = N_2$

    (D) $N_1 = 0$

56. In an AC circuit, if the phase difference between current $I$ and voltage $V$ is $\phi$, the wattless component of current will be: [BSEB, 2021 (A)]

    (A) $I \cos \phi$

    (B) $I \sin \phi$

    (C) $I \tan \phi$

    (D) $I \cos^2 \phi$

57. Dimension of $\frac{L}{R}$ is same as that of: [BSEB, 2018 (A)]

    (A) Frequency

    (B) Time

    (C) Velocity

    (D) Angular velocity

58. Working principle of a choke coil is based on: [BSEB, 2024 (A)]

    (A) Self-induction

    (B) Mutual induction

    (C) Eddy currents

    (D) None of these

59. Hot wire ammeter measures which value of alternating current? [BSEB, 2016 (A)]

    (A) Peak value

    (B) Average value

    (C) Root-mean-square value (rms)

    (D) None of these

60. The average value of alternating current in a full cycle is: [BSEB, 2024 (A)]

    (A) Zero

    (B) $2I_0/\pi$

    (C) $I_0/2$

    (D) $I_0/\sqrt{2}$

Unit 5: Electromagnetic Waves

61. The direction of propagation of electromagnetic waves is: [BSEB, 2021 (A)]

    (A) Parallel to $\vec{B}$

    (B) Parallel to $\vec{E}$

    (C) Parallel to $\vec{B} \times \vec{E}$

    (D) Parallel to $\vec{E} \times \vec{B}$

62. Nature of electromagnetic waves is: [BSEB, 2020 (A)]

    (A) Transverse

    (B) Longitudinal

    (C) Both transverse and longitudinal

    (D) Mechanical

63. Relation between speed of light $c$ in vacuum and $\mu_0, \epsilon_0$ is: [BSEB, 2021 (A)]

    (A) $c = 1 / \sqrt{\mu_0 \epsilon_0}$

    (B) $c = \sqrt{\mu_0 \epsilon_0}$

    (C) $c = \mu_0 \epsilon_0$

    (D) $c = 1 / \mu_0 \epsilon_0$

64. Which of the following has the highest frequency? [BSEB, 2023 (A)]

    (A) Gamma rays

    (B) X-rays

    (C) Ultraviolet rays

    (D) Infrared rays

65. Which of the following has the minimum wavelength? [BSEB, 2023 (A)]

    (A) Gamma rays

    (B) Radio waves

    (C) Visible light

    (D) Microwaves

66. Formula for displacement current ($i_d$) is: [BSEB, 2024 (A)]

    (A) $i_d = \epsilon_0 \frac{d\Phi_E}{dt}$

    (B) $i_d = \mu_0 \frac{d\Phi_E}{dt}$

    (C) $i_d = \frac{1}{\epsilon_0} \frac{d\Phi_E}{dt}$

    (D) $i_d = \epsilon_0 \frac{dt}{d\Phi_E}$

67. Ozone layer absorbs which rays? [BSEB, 2019 (A)]

    (A) Ultraviolet rays

    (B) Infrared rays

    (C) X-rays

    (D) Gamma rays

68. Waves used in Radar systems are: [BSEB, 2021 (A)]

    (A) Microwaves

    (B) Ultraviolet rays

    (C) Radio waves

    (D) Visible light

69. Unit of $\sqrt{\frac{\mu_0}{\epsilon_0}}$ is: [BSEB, 2025 (A)]

    (A) Newton/Coulomb

    (B) Ohm

    (C) Henry

    (D) Farad

70. Radiation suitable for telecommunication is: [BSEB, 2026]

    (A) Ultraviolet

    (B) Visible light

    (C) X-rays

    (D) Microwaves

71. Main cause of production of electromagnetic waves is: [BSEB, 2016 (A)]

    (A) Accelerated charge

    (B) Stationary charge

    (C) Charge moving with uniform velocity

    (D) Current carrying conductor

72. Remote control of Television uses: [BSEB, 2026]

    (A) Infrared waves

    (B) Ultraviolet waves

    (C) Radio waves

    (D) Microwaves

73. Dimension of $\frac{B_0^2}{2\mu_0}$ is equivalent to: [BSEB, 2018 (A)]

    (A) $1/2 \epsilon_0 E^2$

    (B) $1/2 \mu_0 E^2$

    (C) $\epsilon_0^2 E$

    (D) $E^2/\epsilon_0$

74. Film used for photography in fog is: [BSEB, 2021 (A)]

    (A) Polaroid

    (B) Infrared

    (C) Ultraviolet

    (D) Ordinary

75. Who first explained electromagnetic waves mathematically? [BSEB, 2026]

    (A) Maxwell

    (B) Hertz

    (C) Faraday

    (D) Marconi

Unit 6: Optics

76. Speed of light in air is $c$, its speed in glass ($\mu = 1.5$) will be: [BSEB, 2021 (A)]

    (A) $3c/2$

    (B) $2c/3$

    (C) $c/2$

    (D) $4c/3$

77. Optical path is equal to: [BSEB, 2021 (A)]

    (A) Refractive index $\times$ Path length

    (B) Path length / Refractive index

    (C) Refractive index / Path length

    (D) $\sqrt{\text{Refractive index}} \times \text{Path length}$

78. Critical angle for diamond is: [BSEB, 2021 (A)]

    (A) $24.41^\circ$

    (B) $37.31^\circ$

    (C) $48.75^\circ$

    (D) $41.14^\circ$

79. Equivalent lens of two convex lenses in contact is: [BSEB, 2021 (A)]

    (A) Convex

    (B) Concave

    (C) Plano-concave

    (D) Cylindrical

80. Least distance of distinct vision for a normal eye is: [BSEB, 2021 (A)]

    (A) 100 cm

    (B) 50 cm

    (C) 250 cm

    (D) 25 cm

81. Cylindrical lens is used to correct which eye defect? [BSEB, 2020 (A)]

    (A) Myopia

    (B) Hypermetropia

    (C) Astigmatism

    (D) Presbyopia

82. Cause of color of light is: [BSEB, 2021 (A)]

    (A) Its frequency

    (B) Its velocity

    (C) Its phase

    (D) Its amplitude

83. Spectrum of sunlight is: [BSEB, 2021 (A)]

    (A) Continuous

    (B) Line spectrum

    (C) Black line spectrum

    (D) Black band spectrum

84. Final image in an astronomical telescope is: [BSEB, 2021 (A)]

    (A) Real and erect

    (B) Real and inverted

    (C) Virtual and inverted

    (D) Virtual and erect

85. Focal length of the lens of a normal human eye is about: [BSEB, 2021 (A)]

    (A) 1 mm

    (B) 2 cm

    (C) 25 cm

    (D) 1 m

86. Dispersive power ($\omega$) is correctly given by: [BSEB, 2021 (A)]

    (A) $\omega = (\mu_V – \mu_R)/(\mu_Y – 1)$

    (B) $\omega = (\mu_Y – 1)/(\mu_V – \mu_R)$

    (C) $\omega = (\mu_V + \mu_R)/(\mu_Y – 1)$

    (D) $\omega = (\mu_V – \mu_Y)/(\mu_R – 1)$

87. Cause of blue color of sky is: [BSEB, 2020 (A)]

    (A) Scattering of light

    (B) Interference of light

    (C) Diffraction of light

    (D) Polarization of light

88. Cause of Mirage is: [BSEB, 2020 (A)]

    (A) Total internal reflection

    (B) Diffraction

    (C) Scattering

    (D) Interference

89. Phase difference for constructive interference is: [BSEB, 2021 (A)]

    (A) $\phi = 2n\pi$

    (B) $\phi = (2n+1)\pi$

    (C) $\phi = n\pi$

    (D) $\phi = n\pi/2$

90. Transverse nature of light waves is confirmed by: [BSEB, 2020 (A)]

    (A) Interference

    (B) Diffraction

    (C) Polarization

    (D) Refraction

91. Radius of curvature of a plane mirror is: [BSEB, 2021 (A)]

    (A) Infinity

    (B) Zero

    (C) 100 cm

    (D) 5 cm

92. SI unit of power of a lens is: [BSEB, 2021 (A)]

    (A) Joule

    (B) Dioptre

    (C) Candela

    (D) Watt

93. Magnifying power of a simple microscope is: [BSEB, 2021 (A)]

    (A) $1 + D/f$

    (B) $D/f$

    (C) $1 + f/D$

    (D) $f/D$

94. Length ($L$) of an astronomical telescope is: [BSEB, 2020 (A)]

    (A) $f_o + f_e$

    (B) $f_o – f_e$

    (C) $f_o \cdot f_e$

    (D) $f_o / f_e$

95. Phenomenon that proves the transverse nature of light is: [BSEB, 2017 (A)]

    (A) Interference

    (B) Diffraction

    (C) Polarization

    (D) Refraction

96. Soap bubble appears colored due to: [BSEB, 2023 (A)]

    (A) Interference

    (B) Diffraction

    (C) Scattering

    (D) Polarization

97. Brewster’s law is: [BSEB, 2021 (A)]

    (A) $\mu = \tan i_p$

    (B) $\mu = \sin i_p$

    (C) $\mu = \cos i_p$

    (D) $\mu = \cot i_p$

98. When the tube length of a microscope is increased, its magnifying power: [BSEB, 2026]

    (A) Increases

    (B) Decreases

    (C) Becomes zero

    (D) Remains unchanged

99. Lens used to correct hypermetropia is: [BSEB, 2026]

    (A) Convex

    (B) Concave

    (C) Cylindrical

    (D) Plano-convex

100. Refractive index of water is 1.33. What will be the speed of light in water? [BSEB, 2026]

     (A) $2.25 \times 10^8 \, m/s$

     (B) $3 \times 10^8 \, m/s$

     (C) $1.5 \times 10^8 \, m/s$

     (D) $4 \times 10^8 \, m/s$

Unit 7: Dual Nature of Radiation & Matter

101. Energy of a photon ($E$) is: [BSEB, 2021 (A)]

     (A) $hv$

     (B) $hc$

     (C) $h/v$

     (D) $v/h$

102. Rest mass of a photon is: [BSEB, 2021 (A)]

     (A) Zero

     (B) Infinity

     (C) $9.1 \times 10^{-31} \, kg$

     (D) $1.6 \times 10^{-27} \, kg$

103. Electron-volt (eV) measures: [BSEB, 2021 (A)]

     (A) Charge

     (B) Potential difference

     (C) Current

     (D) Energy

104. De-Broglie wavelength ($\lambda$) is: [BSEB, 2021 (A)]

     (A) $h/mv$

     (B) $mv/h$

     (C) $h \cdot mv$

     (D) $v/hm$

105. Kinetic energy of emitted electrons in photoelectric effect depends on: [BSEB, 2024 (A)]

     (A) Frequency of light

     (B) Intensity of light

     (C) Work function of metal

     (D) Both (A) and (C)

106. Value of Planck’s constant ($h$) is: [BSEB, 2021 (A)]

     (A) $6.63 \times 10^{-34} \, J \cdot s$

     (B) $6.63 \times 10^{-31} \, J \cdot s$

     (C) $6.63 \times 10^{-34} \, J/s$

     (D) $6.63 \times 10^{-31} \, J/s$

107. Work function is minimum for which of the following? [BSEB, 2024 (A)]

     (A) Iron

     (B) Copper

     (C) Caesium

     (D) Gold

108. Cathode rays are a group of: [BSEB, 2021 (A)]

     (A) Electrons

     (B) Protons

     (C) Neutrons

     (D) Atoms

109. Photo cell is based on: [BSEB, 2024 (A)]

     (A) Photoelectric effect

     (B) Heating effect of current

     (C) Chemical effect

     (D) Magnetic effect

110. Relation between de-Broglie wavelength ($\lambda$) and momentum ($p$) is: [BSEB, 2026]

     (A) $\lambda = h/p$

     (B) $\lambda = p/h$

     (C) $\lambda = hp$

     (D) $\lambda = p^2h$

Unit 8: Atoms & Nuclei

111. 111. Nucleus of an atom is made of: [BSEB, 2024 (A)]

          (A) Protons and neutrons

          (B) Protons and electrons

          (C) Protons only

          (D) Neutrons and electrons

     112. Which series of hydrogen spectrum lies in the visible region? [BSEB, 2021 (A)]

          (A) Lyman series

          (B) Balmer series

          (C) Paschen series

          (D) Brackett series

113. Relation between radius of nucleus ($R$) and mass number ($A$) is: [BSEB, 2021 (A)]

     (A) $R \propto A^{1/3}$

     (B) $R \propto A^{1/2}$

     (C) $R \propto A$

     (D) $R \propto A^{2/3}$

114. Half-life ($T_{1/2}$) of a radioactive substance is: [BSEB, 2021 (A)]

     (A) $0.693/\lambda$

     (B) $\lambda/0.693$

     (C) $0.693 \cdot \lambda$

     (D) $1/\lambda$

115. $\alpha$-particle is: [BSEB, 2021 (A)]

     (A) Electron

     (B) Helium nucleus

     (C) Hydrogen nucleus

     (D) Proton

116. Source of solar energy is: [BSEB, 2021 (A)]

     (A) Nuclear fission

     (B) Nuclear fusion

     (C) Chemical reaction

     (D) None of these

117. 1 amu (Atomic Mass Unit) is equal to: [BSEB, 2021 (A)]

     (A) $1.6 \times 10^{-27} \, kg$

     (B) $1.6 \times 10^{-31} \, kg$

     (C) $1.6 \times 10^{-24} \, kg$

     (D) $1.6 \times 10^{-19} \, kg$

118. Which of the following relations is correct? [BSEB, 2021 (A)]

     (A) $1 \, amu = 931 \, MeV$

     (B) $1 \, amu = 931 \, eV$

     (C) $1 \, amu = 931 \, J$

     (D) $1 \, amu = 1.6 \times 10^{-19} \, J$

119. Which force keeps electrons inside the atom? [BSEB, 2026]

     (A) Gravitational force

     (B) Nuclear force

     (C) Coulomb force

     (D) Magnetic force

120. $\beta$-rays are deflected in: [BSEB, 2020 (A)]

     (A) Gravitational field

     (B) Only magnetic field

     (C) Only electric field

     (D) Both magnetic and electric fields

121. Bohr’s principle of angular momentum is: [BSEB, 2021 (A)]

     (A) $L = nh/2\pi$

     (B) $L = nh/\pi$

     (C) $L = 2\pi/nh$

     (D) $L = n^2h/2\pi$

122. Highest penetrating power is of: [BSEB, 2021 (A)]

     (A) $\alpha$-rays

     (B) $\beta$-rays

     (C) $\gamma$-rays

     (D) Cathode rays

123. Moderator in a nuclear reactor is: [BSEB, 2024 (A)]

     (A) Heavy water ($D_2O$)

     (B) Graphite

     (C) Cadmium

     (D) Both (A) and (B)

124. Unit of radioactivity is: [BSEB, 2023 (A)]

     (A) Curie

     (B) Becquerel

     (C) Rutherford

     (D) All of the above

125. Energy of electron in 1st orbit of H-atom is -13.6 eV. Energy in 2nd orbit will be: [BSEB, 2026]

     (A) -3.4 eV

     (B) -6.8 eV

     (C) -27.2 eV

     (D) -1.51 eV

Unit 9: Electronic Devices

126. 126. Majority charge carriers in $p$-type semiconductor are: [BSEB, 2021 (A)]

          (A) Electrons

          (B) Holes

          (C) Photons

          (D) Protons

     127. Majority charge carriers in $n$-type semiconductor are: [BSEB, 2021 (A)]

          (A) Electrons

          (B) Holes

          (C) Alpha-particles

          (D) Protons

     128. Boolean expression for NAND gate is: [BSEB, 2021 (A)]

          (A) $\overline{A \cdot B} = Y$

          (B) $A \cdot B = Y$

          (C) $\overline{A + B} = Y$

          (D) $A + B = Y$

     129. Boolean expression for NOR gate is: [BSEB, 2021 (A)]

          (A) $\overline{A + B} = Y$

          (B) $A + B = Y$

          (C) $\overline{A \cdot B} = Y$

          (D) $A \cdot B = Y$

     130. Decimal value of binary number $(1001)_2$ will be: [BSEB, 2021 (A)]

          (A) 9

          (B) 10

          (C) 11

          (D) 12

     131. Basic gates are: [BSEB, 2021 (A)]

          (A) AND, OR, NOT

          (B) NAND, NOR

          (C) OR, NOT

          (D) AND, OR

132. Diode is used as a: [BSEB, 2021 (A)]

     (A) Amplifier

     (B) Oscillator

     (C) Rectifier

     (D) Modulator

133. Width of forbidden energy gap in a semiconductor is about: [BSEB, 2022 (A)]

     (A) $1 \, eV$

     (B) $5 \, eV$

     (C) $10 \, eV$

     (D) $15 \, eV$

134. Binary equivalent of decimal number 25 is: [BSEB, 2020 (A)]

     (A) $(11001)_2$

     (B) $(10011)_2$

     (C) $(11010)_2$

     (D) $(11101)_2$

135. Thickness of depletion layer in a P-N junction diode is: [BSEB, 2024 (A)]

     (A) $10^{-6} \, m$

     (B) $10^{-4} \, m$

     (C) $10^{-10} \, m$

     (D) $10^{-2} \, m$

136. Boolean expression for AND gate is: [BSEB, 2021 (A)]

     (A) $A \cdot B = Y$

     (B) $A + B = Y$

     (C) $\overline{A \cdot B} = Y$

     (D) $\overline{A + B} = Y$

137. Zener diode is used for: [BSEB, 2023 (A)]

     (A) Voltage regulation

     (B) Amplification

     (C) Rectification

     (D) Oscillation

138. Relation between current gains $\alpha$ and $\beta$ in a transistor is: [BSEB, 2024 (A)]

     (A) $\beta = \alpha / (1-\alpha)$

     (B) $\alpha = \beta / (1+\beta)$

     (C) $\beta = \alpha / (1+\alpha)$

     (D) Both (A) and (B)

139. If input frequency in a full-wave rectifier is $50 \, Hz$, the output frequency will be: [BSEB, 2026]

     (A) $50 \, Hz$

     (B) $100 \, Hz$

     (C) $25 \, Hz$

     (D) $200 \, Hz$

140. Solar cell panels are used in: [BSEB, 2022 (A)]

     (A) Artificial satellites

     (B) Houses for lighting

     (C) Calculators

     (D) All of the above

Unit 10: Communication Systems

141. Frequency range used for TV transmission is: [BSEB, 2021 (A)]

     (A) $30 – 300 \, Hz$

     (B) $30 – 300 \, kHz$

     (C) $30 – 300 \, MHz$

     (D) $30 – 300 \, GHz$

142. Reverse process of modulation is called: [BSEB, 2022 (A)]

     (A) Demodulation

     (B) Transmission

     (C) Repeating

     (D) Attenuation

143. Propagation of Sky waves is based on: [BSEB, 2018 (A)]

     (A) Reflection by ionosphere

     (B) Absorption by ionosphere

     (C) Transmission through ionosphere

     (D) None of these

144. Value of amplitude modulation index lies between: [BSEB, 2021 (A)]

     (A) Always zero

     (B) 1 and $\infty$

     (C) 0 and 1

     (D) Always 1

145. FAX stands for: [BSEB, 2018 (A)]

     (A) Full Access Transmission

     (B) Facsimile Telegraphy

     (C) Factual Auto Access

     (D) Feedback Auto Exchange

146. Space waves are used in: [BSEB, 2026]

     (A) Line of Sight (LOS) communication

     (B) Satellite communication

     (C) Both (A) and (B)

     (D) None of these

147. Height of a TV transmission tower at a place is $245 \, m$. Maximum distance up to which the broadcast will reach is: [BSEB, 2024 (A)]

     (A) $245 \, m$

     (B) $24.5 \, km$

     (C) $56 \, km$

     (D) $112 \, km$

148. Digital signals use: [BSEB, 2026]

     (A) 0 and 1

     (B) All digits from 0 to 9

     (C) Only 0

     (D) Only 1

149. On which principle does Optical Fibre work? [BSEB, 2021 (A)]

     (A) Refraction

     (B) Diffraction

     (C) Total Internal Reflection

     (D) Scattering

150. For long distance radio broadcasting, which of the following is used? [BSEB, 2024 (A)]

     (A) Ground waves

     (B) Line of Sight waves

     (C) Ionospheric waves

     (D) Satellite communication