1. Mechanics
    2. 1. Units, Dimensions and Errors
    2. Vectors and Scalars
    3. Motion in a Straight Line
    4. Projectile Motion
    5. Newton's Laws of Motion
    6. Friction
    7. Work, Energy, Power and Collision
    8. Circular motion
    9. Rotational motion
    10. Simple Harmonic Motion
    11. Gravitation
    12. Elasticity
    13. Surface Tension
    14. Fluid dynamics and Viscosity
    15. Hydrostatics
  2. Heat and Thermodynamics
    3. 16. Thermometry
    17. Thermal expansion
    18. Calorimetry, Change of State and Hygrometry
    19. Gas Laws and Kinetic theory of Gases
    20. Transmission of Heat
    21. Thermodynamics
  3. Sound and Waves
    4. 22. Wave
    23. Superposition of Waves
    24. Stationary/ Standing waves
    25. Doppler's effect and Musical sound
  4. Optics
    5. 26. Reflection of Plane and Curved Mirrors
    27. Refraction at Plane surfaces and Total internal reflection
    28. Refraction through prism and Dispersion of Light
    29. Refraction through Lenses
    30. Chromatic abberation in Lenses, Optical instruments and Human eye
    31. Velocity of Light
    32. Photometry
    33. Wave nature of Light
  5. Electrostatics
    6. 34. Charge and Force
    35. Electric Field and Potential
    36. Capacitance
  6. Electrodynamics
    7. 37. Electric current
    38. Heating Effect of Current
    39. Thermoelectricity
    40. Chemical effect of Current
    41. Meters
  7. Electromagnetism
    8. 42. Properties of Magnets
    43. Magnetic effects of Current
    44. Electromagnetic induction
    45. Alternating current
  8. Modern Physics
    9. 46. Cathode rays, Positive rays and Electrons
    47. Photoelectric effect
    48. X-rays
    49. Atomic structure and Spectrum
    50. Radioactivity
    51. Nuclear physics
    52. Semiconductor and Semiconductor devices
    53. Diode and Triode valves
    54. Logic gates
    55. Relativity and Universe
    56. Particle physics
Modern Physics
47. Photoelectric effect
1. If a photon has 100 eV energy then its frequency is

[TOM 2009]

  • 2.5 × 1015 Hz
  • 2.5 × 1010 Hz
  • 2.5 × 1024 Hz
  • 2.5 × 1032 Hz
2. Planck's constant has the dimension of

[MOE 2013]

  • energy
  • mass
  • frequency
  • angular momentum
3. If a pd of 1V is applied across an electron, the energy gained by it will be

[MOE 2012]

  • 1 J
  • 1 eV
  • 1 Nm
  • 1 watt sec
4. Electron, proton, neutron and alpha particle have the same K.E. Which has the highest de-Broglie wavelength?

[MOE 2012 & 2068]

  • electron
  • proton
  • neutron
  • alpha particle
5. A metal (work function 3.31 eV) is illuminated by light of wavelength 5×10-7 m. The threshold frequency is:

[MOE 2010]

  • 8 × 1014 Hz
  • 1.6 × 1015 Hz
  • 2.4 × 1015 Hz
  • 3.2 × 1015 Hz
6. Light (λ=400nm) on metal (threshold λ=600nm) produces current I. If λ is doubled, photoelectric current will be:

[MOE 2068]

  • I
  • 2I
  • I/2
  • Zero
7. If K.E. of a particle increases by four times, de-Broglie wavelength becomes:

[MOE 2010]

  • 2 times
  • 1/2 times
  • 1/4 times
  • √2 times
8. The de-Broglie wavelength of electron is 1.224 Å. The energy of electron in eV is:

[MOE 2010]

  • 1
  • 10
  • 100
  • 1224
9. An electron (mass 'm', charge 'e') is accelerated from rest through pd. 'V' volts. Its speed will be:
  • √(eV/m)
  • √(2eV/m)
  • V/m
  • eV/m
10. In photoelectric effect, the number of ejected electrons per second depends on:

[KU 2012]

  • frequency of incident radiation
  • intensity of incident radiation
  • wavelength of incident radiation
  • time of exposure
11. The wavelength associated with an electron (mass m, velocity v) is:

[KU 2011]

  • h/mv
  • mv/h
  • √(mv/h)
  • h/√(mv)
12. Work function = 2 eV. Velocity of emitted electron when λ=230 nm light is incident?

[KU 2010]

  • 1.1 × 106 m/s
  • 2 × 106 m/s
  • 1 × 106 m/s
  • 7 × 106 m/s
13. Which wavelength falls under visible light?
  • 900 Å
  • 640 nm
  • 640 Å
  • 900 Å
14. Which has frequency 6 × 1015 Hz?

[BP 2012]

  • Radio waves
  • UV-rays
  • Microwaves
  • X-rays
15. Two photons traveling opposite directions have relative velocity:

[I.E. 2009]

  • c
  • 2c
  • c/2
  • 0
16. Photoelectric effect is explained by:

[I.E. 2009]

  • Wave theory only
  • EM theory only
  • Quantum theory only
  • None
17. An α-particle and proton accelerated through same potential. Ratio of final velocities:

[I.E. 2011]

  • √2 : 1
  • 1 : √2
  • 1 : 2
  • 2 : 1
18. Particle nature of light is shown by:

[TOM 2014]

  • Photoelectric effect
  • Velocity of light
  • Diffraction
  • Refraction
19. Light (1.5× threshold frequency) on material. If frequency is halved and intensity doubled, photocurrent becomes:

[MOE 2014]

  • Quadrupled
  • Doubled
  • Halved
  • Zero
20. What will be the maximum velocity of photoelectrons ejected from a metal (work function 1eV) when light of wavelength 3000Å falls on it?

[MOE 2014]

  • 103 m/s
  • 104 m/s
  • 105 m/s
  • 106 m/s
21. Which phenomenon does NOT support the wave theory of light?

[BP 2014]

  • Polarization
  • Interference
  • Diffraction
  • Photoelectric effect
22. If threshold frequency increases, what happens to the K.E. of photoelectrons?

[BP 2014]

  • Increases
  • Decreases
  • Remains constant
  • First increases then decreases
23. Value of Planck’s constant (h) is:

[BP 2014]

  • 6.625 × 10-34 Js
  • 6.625 × 10-27 Js
  • 6.625 × 10-20 Js
  • 6.625 × 10-10 Js
24. Uncertainty in proton position is 6×10-8 m. Minimum uncertainty in speed is:

[BP 2014]

  • 1 cm/s
  • 1 m/s
  • 1 mm/s
  • 100 m/s
25. Ratio of de Broglie wavelengths of proton and α-particle with same K.E.:

[BP 2014]

  • 2 : 1
  • 1 : 2
  • 1 : √2
  • √2 : 1
26. Work function = 3.3 eV. Threshold frequency is:

[MOE 066]

  • 8 × 1014 Hz
  • 8 × 1015 Hz
  • 8 × 1016 Hz
  • 5 × 1020 Hz
27. UV photon (work function = 2 eV) produces photoelectron with 2 eV energy. Photon wavelength is:

[MOE 2065]

  • 9300 Å
  • 6200 Å
  • 4900 Å
  • 3100 Å
28. Photoelectric effect conserves:

[MOE 2063]

  • Energy
  • Momentum
  • Angular momentum
  • Power
29. Light (frequency 3ν0) on material. If frequency is halved and intensity doubled, photocurrent becomes:
  • Zero
  • Halved
  • Quadrupled
  • Doubled
30. Behind cutoff voltage, photoelectron emission is proportional to:

[I.E. 06]

  • Voltage
  • K.E.
  • Number of photons
  • Field
31. Photoelectrons from a monochromatic beam have:

[BPKIHS-08]

  • Energy spread with no sharp limits
  • Energy spread with a lower limit
  • Definite energy only
  • Energy spread with an upper limit
32. Increasing light intensity affects:

[BPKIHS 02]

  • Photocurrent increases
  • Frequency increases
  • Maximum K.E. increases
  • Photocurrent decreases
33. When frequency increases:

[BPKIHS 02]

  • Photocurrent increases
  • Maximum K.E. increases
  • Stopping potential decreases
  • Photocurrent decreases
34. Photocell current is:

[BPKIHS-04]

  • Directly proportional to intensity
  • Directly proportional to square of intensity
  • Inversely proportional to square of intensity
  • Inversely proportional to intensity
35. UV radiation (6.2 eV) on aluminum (φ = 4.2 eV). K.E.max is:

[BPKIHS 05]

  • 4.2 × 10-17 J
  • 3 × 10-17 J
  • 1.4 × 10-17 J
  • 2.65 × 10-17 J
36. Photoelectric effect occurs if incident light frequency is:

[BPKIHS 05]

  • Greater than threshold frequency
  • Less than threshold frequency
  • Equal to threshold frequency
  • Equal to heat radiation frequency
37. Photoelectric effect proves the existence of:
  • Electrons
  • EM fields
  • Protons
  • Photons
38. Number of photons for fixed energy varies:
  • Inversely with wavelength
  • Inversely with frequency
  • Directly with frequency
  • Independent of frequency
39. X-ray photon (λ = 0.01 Å) momentum is:

[MOE 2008]

  • 6.6 × 10-22 kg m/s
  • 6.6 × 10-32 kg m/s
  • 3.3 × 10-32 kg m/s
  • 0
40. Energy of green light photon (λ = 5000 Å) is:
  • 3.459 × 10-19 J
  • 4.132 × 10-19 J
  • 3.973 × 10-19 J
  • 8.453 × 10-19 J
41. Energy of photon (λ = 6600 Å) in eV is:
  • 0.1875 eV
  • 1.875 eV
  • 18.75 eV
  • 198 eV
42. Radio transmitter (1000 kHz, 66W) emits how many photons/second?
  • 1020
  • 1025
  • 1029
  • 1030
43. Light (1.5× threshold frequency). If frequency is halved, photoelectrons:
  • Four times
  • Doubled
  • Halved
  • Zero
44. Threshold frequency = ν0. If incident frequency doubles, K.E. becomes:
  • Doubled
  • Halved
  • More than doubled
  • Less than doubled
45. If light frequency doubles in photoelectric experiment, stopping potential:
  • Doubles
  • Halves
  • More than doubles
  • Less than doubles
46. Threshold wavelength = 5000 Å. Photoemission occurs with:
  • 50W infrared lamp
  • 1W infrared lamp
  • 0.5W infrared lamp
  • 50W ultraviolet lamp
47. Threshold wavelength = 5200 Å. Photoemission occurs with:
  • 50W infrared lamp
  • 25W red light lamp
  • 50W green light lamp
  • All of above
48. Photon energy = 6 eV, maximum K.E. = 4 eV. Stopping potential is:
  • 2 V
  • 4 V
  • 6 V
  • 8 V
49. Green light ejects electrons; yellow does not. Red light will:
  • Emit more energetic electrons
  • Emit less energetic electrons
  • Depend on intensity
  • Not emit electrons
50. Stopping potential is V when λ = λ. For λ = 2λ, stopping potential = V/3. Threshold λ is:
  • 4λ/3
  • 3λ/2
  • 2λ
  • 4λ
51. Photoelectrons have K.E. ratio 1:K for frequencies ν1 and ν2 (ν1 > ν2). Threshold frequency is:
  • (ν1 - Kν2)/(1 - K)
  • (Kν2 - ν1)/(K - 1)
  • (ν1 + Kν2)/(1 + K)
  • (Kν1 - ν2)/(K - 1)
52. Work function = 2.2 eV. Maximum wavelength for photoemission is:

[MOE Bangladesh 2009]

  • 597 nm
  • 567 nm
  • 546 nm
  • 967 nm
53. Radiation with photon energies 2φ and 10φ incident on metal. Ratio of maximum photoelectron velocities:
  • 1 : 4
  • 1 : 2
  • 1 : 1
  • 1 : 3
54. Photon energy = 5 eV, threshold frequency = 1.6 × 1015 Hz. K.E. of photoelectron (in eV):

[KU 2014]

  • 6
  • 1.6
  • 1.2
  • 2
55. Cutoff potential = V0 at 1m. If source is moved to 2m, cutoff potential becomes:
  • 2V0
  • V0/2
  • V0
  • V0/4
56. Speed of electron with λ = 10-10 m is:
  • 7.25 × 106 m/s
  • 5.25 × 106 m/s
  • 6.25 × 106 m/s
  • 4.24 × 106 m/s
57. K1 and K2 are maximum K.E. for wavelengths λ1 and λ2. If λ1 = 3λ2, then:

[BP 2014]

  • K1 > K2/3
  • K1 < K2/3
  • K1 = 3K2
  • K2 = 3K1
58. Work functions: A = 1.92 eV, B = 2.0 eV, C = 5 eV. Which emit photoelectrons for λ = 4100 Å?
  • None
  • A only
  • A and B only
  • All three
59. For a metal, ν = 2ν0 gives vmax = 4 × 106 m/s. If ν = 5ν0, vmax will be:
  • 2 × 106 m/s
  • 8 × 106 m/s
  • 2 × 107 m/s
  • 8 × 107 m/s
60. X-rays on sodium and copper surfaces. Stopping potential is:
  • Equal for both
  • Greater for sodium
  • Greater for copper
  • Infinite for both
61. Monochromatic source at distance 'd' emits n electrons/s with K.E. = E. At distance d/2:
  • 2n and 2E
  • 4n and 4E
  • 4n and E
  • n and 4E
62. UV light (λ = 300 nm, I = 1.0 W/m²) on photosensitive material (1% efficiency). Photoelectrons emitted from 1.0 cm² area:
  • 9.61 × 1013 s-1
  • 4.12 × 1011 s-1
  • 1.51 × 1012 s-1
  • 2.13 × 1010 s-1
63. Particle (mass 5m) decays into 2m and 3m. Ratio of de Broglie wavelengths:
  • 1 : 1
  • 2 : 3
  • 3 : 2
  • None
64. Proton and α-particle accelerated through same V. Ratio of de Broglie wavelengths:
  • 1 : 1
  • 2√2 : 1
  • 1 : 2
  • 2 : 1
65. Proton (λ = λ) accelerated through V volt. To get same λ for α-particle, potential needed is:
  • V/8
  • V/4
  • V/2
  • V
66. Particles with same velocity. Maximum de Broglie wavelength is for:
  • Proton
  • α-particle
  • Nucleus
  • β-particle
67. Electron and photon with same λ have same:
  • Energy
  • Linear momentum
  • Angular momentum
  • Speed
68. Energy added to electron to reduce λ from 10-10 m to 0.5 × 10-10 m:
  • Twice initial energy
  • Thrice initial energy
  • Four times initial energy
  • Equal to initial energy
69. Electron and photon have same K.E. = 10-20 J. Their wavelengths relate as:
  • λe = λph
  • λe > λph
  • λe < λph
  • λe = 0
70. Electron accelerated from 20V to 40V. de Broglie wavelength at 40V:
  • 0.75 Å
  • 2.75 Å
  • 2.75 m
  • 7.5 Å
71. de Broglie wavelength order for e-, p, n, α with same K.E.:
  • α < n < p < e-
  • e- < p < n < α
  • p < n < α < e-
  • Cannot compare
72. Initial momentum of electron if momentum change Δp = pm causes 0.5% λ change:
  • 200 pm
  • 100 pm
  • 50 pm
  • 60 pm
73. Ratio of momentum of e- and α accelerated through 100V:
  • √(me/mα)
  • √(2me/mα)
  • √(mα/me)
  • √(mα/2me)
74. de Broglie wavelength of particle (rest mass m0) moving at c:
  • ∞
  • 0
  • m0c/h
  • h/(m0c)
75. Photon momentum = 3.3 × 10-27 kg m/s. Frequency is:
  • 1.5 × 1015 Hz
  • 7.5 × 1015 Hz
  • 6.0 × 1015 Hz
  • 3.0 × 1015 Hz
76. Ratio of de Broglie wavelengths of proton and α with same energy:

[IOM/BPKIHS]

  • 2 : 1
  • 1 : 2
  • 4 : 1
  • 1 : 4
77. de Broglie wavelength of electron in first Bohr orbit:
  • Equal to circumference
  • Equal to twice circumference
  • Equal to half circumference
  • Equal to one-fourth circumference
78. Particle (v = 2.25 × 108 m/s) has same λ as photon. Ratio of K.E./Ephoton:
  • 3/8
  • 1/2
  • 2/3
  • 1/4
79. If K.E. of free electron doubles, de Broglie wavelength changes by factor:
  • √2
  • 1/√2
  • 2
  • 1/2
80. Uncertainty in electron position = 10-10 m. Minimum uncertainty in momentum:
  • 3.3 × 10-24 kg m/s
  • 1.03 × 10-24 kg m/s
  • 6.6 × 10-24 kg m/s
  • 6.6 × 10-20 kg m/s
81. Laser pulse period = 0.25 μs. Uncertainty in energy:
  • 4.2 × 10-9 J
  • 4.2 × 10-12 J
  • 4.2 × 10-15 J
  • 4.2 × 10-30 J
82. Uncertainty in proton speed (Δx = 6 × 10-8 m):
  • 1 cm/s
  • 1 m/s
  • 1 mm/s
  • 100 mm/s
83. Electron velocity accuracy = 0.005%. Position measurement accuracy:
  • 4.634 × 10-4 m
  • 4.634 × 10-5 m
  • 4.634 × 10-6 m
  • 4.634 × 10-7 m
84. Electron excitation time = 10-6 μs. Uncertainty in photon frequency:
  • 1.6 × 108 Hz
  • 1.6 × 109 Hz
  • 1.6 × 1010 Hz
  • 1.6 × 1011 Hz
85. de Broglie wavelength of neutron at 927°C is λ. At 27°C, it is:
  • λ/2
  • λ/√2
  • 2λ
  • λ/4
86. Wavelength of 10 keV electron:
  • 0.12 Å
  • 1.2 Å
  • 12 Å
  • 120 Å
87. Particles A (+q) and B (+4q) with same mass 'm' fall through same V. Ratio vA/vB:
  • 2 : 1
  • 1 : 2
  • 1 : 4
  • 4 : 1
88. de Broglie wavelength of body (mass m, energy E):

[IOM 2015]

  • h/√(2mE)
  • √(h/2mE)
  • h/(2mE)
  • √(2mE)/h
89. Quantum theory is explained by:

[KU 2016]

  • Photon
  • Positron
  • Electron
  • None
90. Radioactive particle decays into two pieces. Ratio of de Broglie wavelengths λ1/λ2:

[IOM 2016]

  • m2/m1
  • √(m2/m1)
  • 1
  • √(m1/m2)