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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
When ultraviolet rays are incident ono metal plate, the photoelectric effect does not occur. It occurs by incidence ofA. infrared raysB. X-raysC. radiowavesD. light waves |
| Answer» Correct Answer - B | |
| 52. |
The de - Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature `T ("kelvin")` and mass `m`, isA. `h/(sqrt(mkT)`B. `h/sqrt(3mkT)`C. `2h/sqrt(3mkT)`D. `2h/sqrt(mkT)` |
| Answer» Correct Answer - B | |
| 53. |
Monochromatic light of wavelength `667 nm` is produced by a helium neon laser . The power emitted is `9 mW` . The number of photons arriving per second on the average at a target irradiated by this beam isA. `9 xx 10^(17)`B. `3 xx 10^(16)`C. `9 xx 10^(15)`D. `3 xx 10^(19)` |
| Answer» Correct Answer - B | |
| 54. |
A photoelectric cell is illuminated by a point source of light `1 m` away . When the source is shifted to `2 m` thenA. each emitted electorns carries half the initial energyB. number of electrons emitted is a quarter of the initial numberC. each emitted electron carries one quarter of the initial energyD. number of electrons emitted is half the initial number |
| Answer» Correct Answer - B | |
| 55. |
Calculate the velocity of a neutron having de Broglie wavelength of 10 fermi. Mass of neutron, `m_(n) = 1.7 xx 10^(-27)kg`. Neglect the relative effects. |
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Answer» Correct Answer - `3.88 xx 10^(7) ms^(-1)` |
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| 56. |
Find the number of photons emitted per second by a 25 W source of monochromatic light of wavelength `6600 Å`. What is the photoelectric current assuming 3% efficiency for photoelectric effect. Given `h = 6.6 xx 10^(-34) Js`. |
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Answer» Correct Answer - `8.33 xx 10^(19), 0.4 A` |
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| 57. |
A photosensitive metallic surface has work function , `h v_(0)`. If photons of energy ` 2hv_(0)` fall on this surface , the electrons come out with a maximum velocity of `4 xx 10^(6) m//s`. When the photon energy is increased to `5hv_(0)` ,then the maximum velocity of photoelectrons will beA. `2 xx 10^(6) m//s`B. `2 xx 10^(7)m//s`C. `8 xx 10^(5) m//s`D. `8 xx 10^(6) m//s` |
| Answer» Correct Answer - D | |
| 58. |
In a discharge tube ionization of enclosed gas is produced due to collisions betweenA. positive ions and neutral atoms/moleculesB. negative electrons and neutral atoms/moleculesC. photons and neutral atoms/moleculesD. neutral gas atoms/molecules |
| Answer» Correct Answer - B | |
| 59. |
Calculate the de-Broglie wavelength associated with an `alpha`-particle accelerated through a potential difference of 200 V. Given `m_(P) = 1.67 xx 10^(-27) kg`. |
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Answer» Correct Answer - `0.007138 Å` |
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| 60. |
In photoelectric effect when photons of energy hv fall on a photosensitive surface (work function hv^) electrons are emitted from the metallic surface with a kinetic energy. It is possible to say that:A. all ejected electrons have same kinetic energy equal to `h v - h v _(0)`B. the ejected electrons have a distribution of kinetic energy from zero `(h v - hv _(0))`C. the most energetic electrons have kinetic energy equal to hvD. all ejected electrons have kinetic energy `hv_(0)` |
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Answer» Correct Answer - B |
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| 61. |
Light of wavelength `5000 Å` falls on a sensitive plate with photoelectric work function of `1.9 eV`. The kinetic energy of the photoelectron emitted will beA. `0.58eV`B. `2.48eV`C. `1.24eV`D. `1.16eV` |
| Answer» Correct Answer - A | |
| 62. |
In the phenomenon of electric discharge through gases at low pressure , the coloured glow in the tube appears as a result ofA. excitation of electrons in the atomsB. collision between the atoms of the gasC. collissions between the charged particles emitted from the cathode and the atoms of the gasD. collission between diferent electrons of the atoms of the gas |
| Answer» Correct Answer - C | |
| 63. |
Electron, initially almost at rest, are accelerated by a potenetial difference of `200` volt. They then pass through an electric field and a magnetic field at right angle to each other and also at right angles to the electron beam. The magnitudes of two fields are so adjusted that the electrons emerge out straight without any deviation. Determine the specific charge, if the electric field is `1117.6` volt `cm^(-1)` and magnetic field is `14` gauss. |
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Answer» Correct Answer - `1.59 xx 10^(11) C g^(-1)` |
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| 64. |
The potential difference through which an electron should be accelerated from rest so that it acquires a speed of `2 xx 10^(7)` m/s isA. 3117 VB. 1137 VC. 3711 VD. 7311 V |
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Answer» Correct Answer - B |
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| 65. |
An electron is projected in a perpendicular uniform magnetic field of `3 xx 10^(-3)` T . If electron moves in circle of radius 4 mm , then linear momentum of electron isA. `1.92 xx 10^(-21)` kg m/sB. `1.92 xx 10^(-24)` kg m/sC. `1.2 xx 10^(-21)` kg m/sD. `3.2 xx 10^(-21) ` kg m/s |
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Answer» Correct Answer - B |
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| 66. |
Kinetic energy of an electron accelerated in a potential difference of `100 V` isA. `1.6 xx 10^(-17)` JB. `1.6 xx 10^(-19)` JC. `1.6 xx 10^(-21)` JD. `1.6 xx 10^(-25)`J |
| Answer» Correct Answer - A | |
| 67. |
In photoelectric effect the work function of a metal is 3.5 eV. The emitted electrons can be stopped by applying a potential of –1.2 V. ThenA. the energy of the incident photons is `4.7eV`B. the energy of the incident photons is `2.3eV`C. if higher frequency photons be used , the photoelectric current will riseD. when the energy of photons is `3.5eV` , the photoelectric current will be maximum |
| Answer» Correct Answer - A | |
| 68. |
Gases begin to conduct electricity at low pressure becauseA. at low pressure gases trun to plasmaB. coliding electrons can acquired higher kinetic energy due to increased mean free path leading to ionisation of atomsC. atoms break up into electronis and protonsD. the electrons in atoms can move freely at low pressure. |
| Answer» Correct Answer - B | |
| 69. |
An electron is accelerated from rest to potential V. the final velocity of electron isA. `sqrt((eV)/(2m))`B. `sqrt((eV)/(m))`C. `sqrt((4eV)/(m))`D. `sqrt((2eV)/(m))` |
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Answer» Correct Answer - D |
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| 70. |
An electron of mass `m` and charge `e` is accelerated from rest through a potential difference `V` in vacuum. The final speed of the electron will beA. `(eV)/(2m)`B. `(eV)/(m)`C. `sqrt((2eV)/(m)`D. `sqrt((ev)/(2m))` |
| Answer» Correct Answer - C | |
| 71. |
Doubly ionised helium atoms and hydrogen ions are accelerated from rest through the same potential drop. The ratio of the final velocities of the helium and the hydrogen ion isA. `1/2`B. 2C. `1/sqrt(2)`D. `sqrt(2)` |
| Answer» Correct Answer - C | |
| 72. |
The work function for a metal surface is 2.0 eV. Determine the longest wavelength that will eject photoelectrons from the metal surface. |
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Answer» Correct Answer - `6000 Å` |
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| 73. |
Work function of metal isA. minimum energy required to free an electron from surface against coulomb forcesB. minimum energy required to free a nucleonC. maximum energy required to eject an electron from electronic orbitD. minimum energy to ionise an atom |
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Answer» Correct Answer - A |
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| 74. |
The work function for photoelectric effectA. depends upon the frequency of incident lightB. is same for all metalsC. is different for different metalsD. none of these |
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Answer» Correct Answer - C |
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| 75. |
Photoelectrons emitted from a metallic surface are those which areA. present inside the nucleusB. are orbiting very near to nucleusC. are generated by the decay of neutrons within the nucleusD. free to move within interatomic spacing |
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Answer» Correct Answer - D |
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| 76. |
Photoelectric effect is described as the ejection of electrons from the surface of a metal when:A. it is heated to a high temperatureB. electrons of suitable velocity impinge on itC. light of suitable wavelength falls on itD. it is placed in a strong magnetic field |
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Answer» Correct Answer - C |
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| 77. |
The photoelectric effect is based on the law of conservation ofA. energyB. linear massC. linear momentumD. angular momentum |
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Answer» Correct Answer - A |
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| 78. |
Photo electric effect can be explained only by assuming that lightA. is a form of transverse wavesB. is a form of longitudinal wavesC. consists of quantaD. can be polarised |
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Answer» Correct Answer - B |
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| 79. |
Photoelectric effect was successfully explained first byA. PlanckB. MaxwellC. EinsteinD. Bohr |
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Answer» Correct Answer - C |
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| 80. |
When a given electromagnetic radiation illuminates the metal surface , the maximum kinetic energy of photoelectrons depends onA. frequency of radiationB. intensity of radiationC. frequency and intensity of radiationD. polarisation of radiation |
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Answer» Correct Answer - A |
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| 81. |
If we consider electrons and photons of same wavelength , then they will have sameA. energyB. velocityC. momentumD. angular momentum |
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Answer» Correct Answer - C |
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| 82. |
If a photoemissive surface has a threshold frequency of `3 xx 10^(14)` Hz, calculate the energy of the photons in eV. |
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Answer» Correct Answer - `12.4 xx 10^(-5) eV` |
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| 83. |
When the energy of the incident radiation is increased by `20 %` , kinetic energy of the photoelectrons emitted from a metal surface increased from `0.5 eV to 0.8 eV`. The work function of the metal isA. `0.65eV`B. `1.0eV`C. `1.3eV`D. `1.5eV` |
| Answer» Correct Answer - B | |
| 84. |
A milliammeter in the circuit of a photoelectric cell measuresA. the photon energyB. the velocity of photoelectronsC. the kinetic energy of photoelectronsD. the number of electrons releases per second |
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Answer» Correct Answer - D |
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| 85. |
A lamp is placed at a distance of 16 cm, from a photocell and the current observed is 1 mA. If the distance from the lamp is reduced to 8 cm, the photocurrent now will beA. 4 mAB. 0.25 mAC. 1m AD. 0.125 mA |
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Answer» Correct Answer - A |
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| 86. |
The radius of circular path of an electron when subjected to a perpendicular magnetic field isA. Be/mvB. mE/BC. me/BD. mv/Be |
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Answer» Correct Answer - D |
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| 87. |
As the intensity of incident light increasesA. photoelectric current increasesB. photoelectric current decreasesC. kinetic energy of photoelectric increasesD. kinetic energy of photoelectrons decreases |
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Answer» Correct Answer - A |
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| 88. |
The photoelectric work function for a metal surface is `4.125 eV`. The cut - off wavelength for this surface isA. `4125 Å`B. `3000 Å`C. `6000 Å`D. `2062.5 Å` |
| Answer» Correct Answer - B | |
| 89. |
As the intensity of incident light increasesA. photocurrent increasesB. photocurrent decreasesC. kinetic energy of emitted photoelectrons increasesD. kinetic energy of emitted photoelectrons decreases |
| Answer» Correct Answer - A | |
| 90. |
Find the strength of the magnetic field required to deflect an electron beam of energy `1//16 MeV` into a circular path of radius `5 cm`. Given `m=9xx10^(-31) kg` and `e=1.6xx10^(-19)C`. |
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Answer» Correct Answer - 0.0168 T |
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| 91. |
The frequency and the intensity of a beam of light falling on the surface of a photoelectric material are increased by a factor of two. This willA. increase the maximum kinetic energy of the photoelectrons as well as photoelectric current by a factor of twoB. increase the maximum kinetic energy of photoelectrons and would increase the photoelectric current by a factor of twoC. increase the maximum kinetic energy of photoelectrons by a factor of two and will have no effect on photoelectric currentD. increase the photoelectric current by a factor of two but will have no effect in kinetic energy of emitted electrons |
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Answer» Correct Answer - B |
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| 92. |
Calculate the energy of a photon in eV for a radio wave of frequency one M Hz. |
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Answer» Correct Answer - `4.14 xx 10^(-9) eV` |
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| 93. |
Of the following properties the photon does not possessA. rest massB. energyC. momentumD. frequency |
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Answer» Correct Answer - A |
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| 94. |
If the energy of a photon is 10 eV , then its momentum isA. `5.33 xx 10^(-23)` kg m/sB. `5.33 xx 10^(-25)` kg m/sC. `5.33 xx 10^(-27)` kg m/sD. `5.33 xx 10^(-29)` kg m/s |
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Answer» Correct Answer - C |
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| 95. |
The rest mass of the photon isA. `9 xx 10^(-31)` kgB. `1.76 xx 10^(-35)` kgC. zeroD. one a.m.u |
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Answer» Correct Answer - C |
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| 96. |
If a photon has velocity c and frequency v , then which of the following represents its wavelength ?A. `(hc)/(E)`B. `(hv)/(E)`C. `(hc)/(c^(2))`D. `hv` |
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Answer» Correct Answer - A |
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| 97. |
The kinetic mass of a photon is given byA. `(hv)/(c^(2))`B. `(c^(2))/(hv)`C. `(hv)/(c)`D. `(c^(2) v)/(h)` |
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Answer» Correct Answer - A |
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| 98. |
Number of electrons emitted by a surface exposed to light is directly proportional toA. velocity of lightB. intensity of lightC. frequency of lightD. wavelength of light |
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Answer» Correct Answer - B |
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| 99. |
In an X-ray tube , electrons bombarding the anode produce X-rays of wavelength 1 Å . The energy of an electron , when it hits the anode isA. `19.8 xx 10^(-16) J`B. `16.3 xx 10^(-16) J`C. `13.7 xx 10^(-16)` JD. `9.8 xx 10^(-16)` J |
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Answer» Correct Answer - A |
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| 100. |
When temperature of a metal increases ,A. K.E. of the electrons increasesB. K.E. of the electrons decreasesC. all the electrons are ejected from the atomD. all the atoms are ionised |
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Answer» Correct Answer - A |
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