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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.
| 1. |
A metallic surface ejects electrons when hit by green light but none when hit by yellow light . Will the electrons be ejected if the same surface is hit by red lightA. yesB. noC. yes, if the red beam is sufficiently intenseD. yes , if the red beam is allowed to fall for sufficient duration |
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Answer» Correct Answer - B |
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| 2. |
An electron of velocity `2.652 xx 10^(7)` m/s enters a uniform magnetic field of direction of motion . The radius of its path isA. 5.3 mmB. 3.5 mmC. 0.3 mmD. 3.0 mm |
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Answer» Correct Answer - C |
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| 3. |
Speed of an electron passing undeviated through a region of cross electric and magnetic fields of magnitude `4 xx 10^(5)` V/m and `0.02 Wb//m^(2)` respectively in meter per second isA. `2 xx 10^(6)`B. `8 xx 10^(7)`C. `8 xx 10^(6)`D. `2 xx 10^(7)` |
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Answer» Correct Answer - D |
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| 4. |
An electron performs uniform circular motion in a region of magnetic field of induction `3 xx 10^(-3) Wb//m^(2)` . If the radius of the circular path of the electron is 2 cm , then the momentum of the electron will beA. `9.6 xx 10^(-24) ` kg m/sB. `6.9 xx 10^(-24)` kg m/sC. `9.6 xx 10^(24)` kg m/sD. `6.9 xx 10^(7)` kg m/s |
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Answer» Correct Answer - A |
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| 5. |
The threshold wavelength for tungsten is 2730 Å . The work function of tungsten isA. `4.5 `eVB. 5.4 eVC. 5.0 eVD. 4.0 eV |
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Answer» Correct Answer - A |
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| 6. |
A `5 W` source emits monochromatic light of wavelength `5000 Å`. When placed `0.5 m` away , it liberates photoelectrons from a photosensitive metallic surface . When the source is moved to a distance of `1.0 m` the number of photoelectrons liberated will be reduced by a factor ofA. 4B. 8C. 16D. 2 |
| Answer» Correct Answer - A | |
| 7. |
If a charge particle of charge q , mass m , moves in a circular path in magnetic field of induction B , under a potential of V volts then radius of circular path isA. `sqrt((2 mV)/(q))`B. `(B)/(1) sqrt((2mV)/(q))`C. `(1)/(B) sqrt((2 m V)/(q))`D. `(1)/(B^(2)) sqrt((2mV)/(q))` |
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Answer» Correct Answer - C |
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| 8. |
Light of frequency `1.5` times the threshold frequency is incident on a photo-sensitive material. If the frequency is halved and the intensity is doubled, the photoelectric current becomesA. quadrupledB. doubledC. halvedD. zero |
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Answer» Correct Answer - D |
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| 9. |
A certain spectral line has wavelength of `4000 Å`. Calculate the frequency and the energy in electron volts of the photons associated with it. |
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Answer» Correct Answer - `7.5 xx 10^(14)Hz, 3.1 eV` |
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| 10. |
The ratio of energy of photon of a wavelength `10^(-10)` m that of photon of wavelength `5 xx 10^(-8)` m isA. `50 : 1`B. ` 200 : 1`C. `500 : 1`D. `100 : 1` |
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Answer» Correct Answer - C |
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| 11. |
When light of wavelength 2000 Å is incident on tungsten the maximum velocity of photoelectrons ejected is observed to be `8 xx 10^(5)` m/s . The threshold wavelength for tungsten isA. 8822 ÅB. 2828 ÅC. 2882 ÅD. 2288 Å |
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Answer» Correct Answer - B |
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| 12. |
In photoelectric effect, stopping potential for a light of frequency `n_(1)` is `V_(1)`. If light is replaced by another having a frequency `n_(2)` then its stopping potential will beA. `V_(1) - (h)/(e) (n_(2) - n_(1))`B. `V_(1) + (h)/(e) (n_(2) + n_(1))`C. `V_(1) + (h)/(e) (n_(2) - 2n_(1))`D. `V_(1) + (h)/(e) (n_(2) - n_(1))` |
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Answer» Correct Answer - D |
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| 13. |
Light of wavelength 5000 Å and intensity of `3.96 xx 10^(-3) watt//cm^(2)` is incident on the surface of photo metal . If 1% of the incident photons only emit photo electrons , then the number of electrons emitted per unit area per second from the surface will beA. `9.82 xx 10^(17) m^(-2)//2`B. `9.82 xx 10^(13) m^(-2) // s`C. `9.82 m^(-2)//s`D. `none of these |
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Answer» Correct Answer - A |
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| 14. |
Wavelength of a `1 ke V` photon is `1.24 xx 10^(-9) m`. What is the frequency of ` 1 Me V` photon ?A. `1.u24 xx 10^(15)`HzB. `2.5 xx 10^(20) Hz`C. `1.24 xx 10^(18)` HzD. `2.4 xx 10^(23)`Hz |
| Answer» Correct Answer - B | |
| 15. |
The threshold wavelength of a metal is 230 nm . The maximum K.E. of the electrons ejected from the metal surface by the radiation of wavelength 180 nanometer isA. 1.5 eVB. 5.1 eVC. 5.5 e VD. 1.0 eV |
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Answer» Correct Answer - A |
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| 16. |
Light of wavelength 2200 Å falls on a metal surface . If 4.1 eV energy is required to remove the electron , find the stopping potential .A. 5.63 VB. 1.53 VC. 6.04 VD. 6.63 V |
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Answer» Correct Answer - B |
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| 17. |
A photon of energy 12 V falls on metal surface whose work function is 4.15 eV . The stopping potential isA. 7.85 VB. 8.75 VC. 7.00 VD. 5.50 V |
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Answer» Correct Answer - A |
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| 18. |
The stopping potential of a photoelectric diode is 9 volts. `e//m = 1.8 xx 10^(11) C kg^(-1)` , then what is its velocity ?A. `1.8 xx 10^(6)` m/sB. `1.8 xx 10^(5)` m/sC. `2.1 xx 10^(5)` m/sD. `1.8 xx 10^(4)` m/s |
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Answer» Correct Answer - A |
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| 19. |
A source `S_(1)` is producing `10^(15)` photons/s of wavelength `5000 Å` Another source `S_(2)` is producing `1.02 xx 10^(15)` photons per second of wavelength `5100 Å`. Then `("power of" `S_(2))/("power of" S_(1))` is equal toA. `1.00`B. `1.02`C. `1.04`D. `0.98` |
| Answer» Correct Answer - A | |
| 20. |
The velocity of photon is proportional to (where v is frequency)A. `v`B. `sqrtv`C. `1//v`D. `v^(2)` |
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Answer» Correct Answer - A |
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| 21. |
In photoelectric emission, the energy of the emitted electron isA. less than that of incident photonB. larger than that of incident photonC. the same as that of incident photonD. proportional to the intensity of incident light |
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Answer» Correct Answer - A |
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| 22. |
The photoelectric work function for potassium is 2 eV . The light of wavelength `3.6 xx 10^(-7)` m falls on potassium . The stopping potential isA. 5.45 voltB. 1.45 voltC. 14.5 voltD. 4.45 volt |
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Answer» Correct Answer - B |
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| 23. |
In photoelectric emission, the velocity of electrons ejected from near the surface isA. same as those coming from interior of metalB. larger than those coming from interior of metalC. less than those coming from interior of metalD. none of these |
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Answer» Correct Answer - B |
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| 24. |
If the photoelectric work function of a metal is 5 eV , the threshold frequency of the metal isA. `2.2 xx 10^(15)` HzB. `1.2 xx 10^(15)` HzC. `1.5 xx 10^(15)` HzD. `5.1 xx 10^(15)` Hz |
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Answer» Correct Answer - B |
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| 25. |
In photoelectric emission process from a metal of work function `1.8 eV` , the kinetic energy of most energetic electrons is `0.5 eV`. The corresponding stopping potential isA. `1.3eV`B. `0.5eV`C. `2.3eV`D. `1.8eV` |
| Answer» Correct Answer - B | |
| 26. |
A charged water drop of weight `4 xx 10^(-18)` kg and charge `1.6 xx 10^(-19)` C is stable in an electric field . What is the intensity of electric fieldA. `150 V m^(-1)`B. `200 V m^(-1)`C. `250 V m^(-1)`D. `50 V m^(-1)` |
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Answer» Correct Answer - C |
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| 27. |
A radio station operates at a frequency of 108.7 MHz with power out put of 250 kW . The rate of emission of quanta from the station isA. `2.0 xx 10^(30)` quanta/sB. `3.4 xx 10^(30)` quanta/sC. `3.4 xx 10^(20)` quanta/sD. `4.3 xx 10^(30)` quanta /s |
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Answer» Correct Answer - B |
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| 28. |
`10^(20)` photons of wavelength 660 nm are emitted per second from a lamp . What is the wattage of the lamp ?A. 30 WB. 60 WC. 100 WD. 500 W |
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Answer» Correct Answer - A |
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| 29. |
How many photons are emitted per second by a 5 mW laser source operating at 632.8 nm? |
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Answer» Correct Answer - `1.6 xx 10^(-16)` |
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| 30. |
Visible light has wavelengths in the range of 400 nm to 780nm. Calculate the range of energy of the photons of visible light. |
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Answer» Correct Answer - `2.56 xx 10^(19) J" to "5.00 xx 10^(-19) J` |
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| 31. |
A stream of electrons moving with a velocity of `6xx10^(7)ms^(-1)` passes between two parallel plates. An electric field of `3000 Vm^(-1)` is applied between the plates. Calculate the strength of the magnetic field required to keep the electron undeflected. |
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Answer» Correct Answer - `5 xx 10^(-5) T` |
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| 32. |
Calculate the frequency of a photon, having energy 41.25 eV. `(h=6.6xx10^(-34) Js)`. |
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Answer» Correct Answer - `10^(15) Hz` |
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| 33. |
An `alpha-`particle of mass `6.65xx10^(-27) kg` travels perpendicular to a magnetic of `0.2 T` with a speed of `6xx10^(5)ms^(-1)`. Calculate the acceleration of the `alpha-`particle. Given the charge on the electron is `1.6xx10^(-19)C`. |
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Answer» Correct Answer - `5.77 xx 10^(12) ms^(-2)` |
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| 34. |
The cathode of a photocell is irradiated with light of wavelength `3000 Å`. The current through the cell is found to stop when the potential of the plate is 2.1 V just below the cathode. Calculate the work function of the cathode. |
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Answer» Correct Answer - 2.04 eV |
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| 35. |
Light from a hydrogen tube is incident on the cathode of a photoelectric cell the work function of the cathode surface is `4.2 eV`. In order to reduce the photo - current to zero the voltage of the anode relative to the cathode must be madeA. `-4.2 V`B. `-9.4 V`C. `-8.4 V`D. `-9.4 V` |
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Answer» Correct Answer - B |
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| 36. |
A charged oil dop is held stationary between the two horizontal plates of a capacitor when a field of 576 kV `m^(-1)` is applied between them. When the field is removed the drop falls freely with a steady velocity of `0.120 xx 10^(-3) ms^(-1)`. Find values for (i) the radius of the drop and (ii) its charge assuming that `6 eta = 0.109 xx 10^(-4) kg m^(-1) s^(-1)` and the difference between the densities of oil and air may be taken as 800 kg `m^(-3)`. |
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Answer» Correct Answer - `(i) 1.12 xx 10^(4) m " "(ii) 797 xx 10^(-19)` coulomb |
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| 37. |
A radio transmitter operates at a frequency of `880 kHz` and a power of `10 kW`. The number of photons emitted per second areA. `1.72 xx 10^(31)`B. `1.327 xx 10^(25)`C. `1.327 xx 10^(37)`D. `1.327 xx 10^(45)` |
| Answer» Correct Answer - A | |
| 38. |
In an oil drop experiment, the following data were recorded : Plate separation = 15 mm, Distance of fall = 10 mm Potential difference = 3.2 kV, Viscosity of air = `1.82 xx 10^(-5)` Ns `m^(-2)` Sucessive times of rise of the drop = 42 s and 78 s. Radius of drop = `2.76 m xx 10^(-6) m` Calculate the change in charge on the drop between the two sets of observation. To how many electrons does this correspond ? |
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Answer» Correct Answer - `4.8 xx 10^(-19) C, 3` |
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| 39. |
The voltage across the electrodes of a cathode ray tube is `1000 V`. Calculate the speed of the electron. Given mass of an electron `=.1xx10^(-31)kg` and charge on electron `=1.6xx10^(16)C`. |
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Answer» Correct Answer - `1.875 xx10^(7)ms^(-1)` |
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| 40. |
An `X-`ray tube operates at `27 kV`. Find the maximum speed of an electron striking the anticathode. Given mass of electron `=9xx10^(31)kg` and charge on electron `=1.6xx10^(-19)C`. |
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Answer» Correct Answer - `9.79xx10^(7)ms^(-1)` |
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| 41. |
The photoelectron emitted from a metal surface are such that their velocityA. is zero for allB. is same for allC. lies between zero to infinityD. lies between zero and a finite maximum |
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Answer» Correct Answer - D |
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| 42. |
What is the momentum of a photon of frequency v ?A. `(hv)/(c^(2))`B. `(hv)/(c)`C. `(v)/(hc)`D. h v c |
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Answer» Correct Answer - B |
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| 43. |
Number of ejected photoelectron increases with increaseA. in intensity of lightB. in wavelength of lightC. in frequency of lightD. never |
| Answer» Correct Answer - A | |
| 44. |
The kinetic energy `(E_(k))` of a photoelectron varies with the frequency (v) of the incident radiation as which of the following graph ?A. B. C. D. |
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Answer» Correct Answer - B |
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| 45. |
Maximum kinetic energy `(E_(k))` of a photoelectron varies with the frequency (v) of the incident radiation asA. B. C. D. |
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Answer» Correct Answer - B |
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| 46. |
The stopping potential as a function of frequency of incident radiation is plotted for two different photoelectric surfaces A and B . The graphs as shown in figure shows that , the work function of A is A. greater than that of BB. smaller than that of BC. same as that of BD. no comparison be made from given graphs |
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Answer» Correct Answer - B |
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| 47. |
When monochromatic light of wavelength `lambda` is incident on a metallic surface the stopping potential for photoelectric current is `3V_(0)` when same surface is illuminated with light of waelength `2lambda` the stopping potential is `V_(0)` The threshold wavelength for this surface when photoelectric effect takes place isA. `lambda`B. `2 lambda`C. `3 lambda`D. `4 lambda` |
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Answer» Correct Answer - D |
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| 48. |
When a metallic surface is illuminated with radiation of wavelength `lambda`, the stopping potential is `V`. If the same surface is illuminated with radiation of wavelength `2 lambda` , the stopping potential is `(V)/(4)`. The threshold wavelength surface is :A. `5lambda`B. `(5)/(2)lambda`C. `3lambda`D. `4lambda` |
| Answer» Correct Answer - C | |
| 49. |
An electron of mass `m` and a photon have same energy `E`. The ratio of de - Broglie wavelengths associated with them is :A. `(E/(em)^(1/2)`B. `c(2mE)^(1/2)`C. `1/c((2m)/E)^(1/2)`D. `1/c(E/2m)^(1/2)` |
| Answer» Correct Answer - D | |
| 50. |
When a certain metallic surface is illuminated with monochromatic light of wavelength `lamda`, the stopping potential for photoelectric current is `3V_0` and when the same surface is illuminated with light of wavelength `2lamda`, the stopping potential is `V_0`. The threshold wavelength of this surface for photoelectrice effect isA. `6lambda`B. `4lambda`C. `lambda/4`D. `lambda/6` |
| Answer» Correct Answer - B | |