Title MODERN PHYSICS I.pdf ✅

NEET : Physics [ 200 ] www.allendigital.in  Digital PHOTO ELECTRIC EFFECT 1. The energy of photon of visible light with maximum wavelength in eV is : (1) 1 (2) 1.6 (3) 3.2 (4) 7 2. What is the momentum of a photon having frequency 1.5 × 1013 Hz : (1) 3.3 × 10–29 kg m/s (2) 3.3 × 10–34 kg m/s (3) 6.6 × 10–34 kg m/s (4) 6.6 × 10–30 kg m/s 3. The strength of photoelectric current is directly proportional to : (1) Frequency of incident radiation (2) Intensity of incident radiation (3) Angle of incidence of radiation (4) Distance between anode and cathode 4. When light is incident on surface, photo electrons are emitted. For photoelectrons : (1) The value of kinetic energy is same for all (2) Maximum kinetic energy do not depend on the wave length of incident light (3) The value of kinetic energy is equal to or less than a maximum kinetic energy (4) None of the above. 5. When light falls on a photosensitive surface, electrons are emitted from the surface. The kinetic energy of these electrons does not depend on the: (1) Wavelength of light (2) Frequency of light (3) Type of material used for the surface (4) Intensity of light 6. The work- function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately : (1) 540 nm (2) 400 nm (3) 310 nm (4) 220 nm 7. Photoelectric effect takes place in element A. Its work function is 2.5 eV and threshold wavelength is . An other element B is having work function of 5 eV. Then find out the maximum wavelength that can produce photoelectric effect in B : (1)  /2 (2) 2 (3)  (4) 3 8. When light of wavelength lesser than 6000 Å is incident on a metal, electrons are emitted. The approximate work-function of the metal is: (1) 1 eV (2) 2 eV (3) 4 eV (4) 6 eV 9. Surface of sodium is illuminated by a light of 6000 Å wavelength. Work function of sodium is 1.6 eV. Then minimum K.E. of emitted electrons is : (1) 0 eV (2) 1.53 eV (3) 2.46 eV (4) 4.14 eV 10. The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential in volt is : (1) 4 (2) 6 (3) 8 (4) 10 11. When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut - off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then :- (1) The stopping potential will be 0.2 V (2) The stopping potential will be 0.6 V (3) The saturation current will be 6 mA (4) The saturation current will be 18 mA 12. The maximum wavelength of light for photoelectric effect from a metal is 200 nm. The maximum kinetic energy of electron which is emitted by the radiation of wavelength 100 nm will be : (1) 12.4 eV (2) 6.2 eV (3) 100 eV (4) 200 eV 13. The stopping potential as a function of frequency of incident radiation is plotted for two different surfaces A and B. The graphs show that the work function of A is VS  A B (1) Greater than that of B (2) Smaller than that of B (3) Same as that of B (4) No comparison can be done from given graphs Exercise - I
Modern Physics  Digital www.allendigital.in [ 201 ] 14. The slope of graph drawn between stopping potential and frequency of incident light for a given surface will be :- (1) h (2) h/e (3) eh (4) e 15. By photo electric effect, Einstein proved :- (1) E = h (2) KE = 1 2 mv2 (3) E = mc2 (4) E = 2 2 Rhc n − 16. Which one among shows particle nature of light? (1) P.E.E. (2) Interference (3) Refraction (4) Polarization 17. A photo-cell is illuminated by a source of light, which is placed at a distance d from the cell, If the distance become d/2, then number of electrons emitted per second will be :- (1) Remain same (2) Four times (3) Two times (4) One-fourth 18. Graph is plotted between maximum kinetic energy of electron with frequency of incident photon in Photo electric effect. The slope of curve will be : Ek  (1) Charge of electron (2) Work function of metal (3) Planck’s constant (4) Ratio of Planck constant and charge of electron 19. Photon of energy 6 eV is incident on a metal surface of work function 4 eV. Maximum KE of emitted photo electrons will be :- (1) 0 eV (2) 1 eV (3) 2 eV (4) 10 eV 20. Light of frequency  is incident on a metal of threshold frequency 0. Then work function of metal will be:- (1) h (2) h0 (3) h( – 0) (4) h ( + 0) 21. The work function of a photo electric material is 3.3 eV. Its threshold frequency will be : (1) 4 × 1023 Hz (2) 8 × 1012 Hz (3) 4 × 1011 Hz (4) 8 × 1014 Hz 22. The value of planck's constant is :– (1) 6.63 × 10–34 J/s (2) 6.63 × 10–34 kg–m2/s (3) 6.63 × 10–34 kg–m2 (4) 6.63 × 10–34 J–s –1 23. When ultraviolet rays incident on metal plate then photoelectric effect does not occur, it occurs by incidence of :– (1) Infrared rays (2) X–rays (3) Radio wave (4) Light wave 24. A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2m then (1) each emitted electron carries one quarter of the initial energy (2) number of electrons emitted is half the initial number (3) each emitted electron carries half the initial energy (4) number of electrons emitted is a quarter of the initial number 25. The graphs show the variation of current I (y-axis) in two photocell A & B as a function of the applied voltage V(x-axis) when light of same frequency is incident on the cell. Which of the following is the correct conclusion drawn from the data ? I A B V (1) Cathodes of the two cells are made from the same substance, the intensity of light used are different (2) Cathodes are made from different substances and the intensity of light is the same (3) Cathode substances as well as intensity of light are different (4) no conclusion can be drawn
NEET : Physics [ 202 ] www.allendigital.in  Digital 26. According to Einstein's photoelectric equation, the graph between the kinetic energy of photoelectrons ejected and the frequency of incident radiation is (1) Frequency Kinetic energy (2) Frequency Kinetic energy (3) Frequency Kinetic energy (4) Frequency Kinetic energy 27. According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal v/s the frequency of the incident radiation gives a straight line whose slope : (1) depends on the intensity of the radiation (2) depends of the nature of the metal used (3) depends both on the intensity of the radiation and the metal used. (4) is the same for all metals and independent of the intensity of the radiation. 28. A photon of energy 4 eV is incident on a metal surface whose work function is 2eV. The minimum reverse potential to be applied for stopping the current is :- (1) 2V (2) 4V (3) 6V (4) 8V MATTER WAVES 29. If E and P are the energy and the momentum of a photon respectively then on reducing the wavelength of photon - (1) P and E both will decrease (2) P and E both will increase (3) P will increase and E will decrease (4) P will decrease and E will increase 30. If the kinetic energy of a moving particle is E, then the De Broglie wavelength is : (1) h 2mE (2) 2mE h (3) h 2mE (4) hE 2mE 31. Electron has energy of 100 eV what will be its wavelength : (1) 1.2 Å (2) 10 Å (3) 100 Å (4) 1 Å 32. The ratio of wavelength of deutron and proton accelerated through the same potential difference will be - (1) 1 2 (2) 2 1 (3) 1 2 (4) 2 1 33. An electron is accelerated from rest, between two points A and B at which the potentials are 20V and 40 V respectively. The De Broglie wavelength associated with the electron at B will be - (1) 0.75 Å (2) 7.5 Å (3) 2.75 Å (4) 2.75 m 34. An electron is moving with velocity 6.6 × 103 m/s. The De-Broglie wavelength associated with electron is (mass of electron = 9 × 10–31 Kg, Plank's Constant = 6.62 × 10–34 J-S) (1) 1 × 10-19 m (2) 1 × 10-5 m (3) 1 × 10-7 m (4) 1 × 10-10 m 35. The energy that should be added to an electron to reduce its De-Broglie wavelength from 10–10m to 0.5 × 10–10 m will be : (1) Four times the initial energy (2) Equal to initial energy (3) Twice the initial energy (4) Thrice the initial energy 36. The magnitude of De broglie wavelength () of electron (e), proton (p), neutron (n) and  - particle () all having the same kinetic energy of 1MeV, in the increasing order will follow the sequence : (1) e, p, n,  (2) e, n, p,  (3) , n, p, e (4) p, e, , n 37. The accelerating voltage of an electron gun is 50,000 volt. De-Broglie wavelength of the electron will be : (1) 0.55 Å (2) 0.055 Å (3) 0.077Å (4) 0.095 Å 38. If the mass of neutron = 1.7 × 10—27 kg. then the De broglie wavelength of neutron of energy 3eV is : (1) 1.6 × 10—10 m (2) 1.6 × 10—11 m (3) 1.4 × 10—10 m (4) 1.4 × 10—11 m
Modern Physics  Digital www.allendigital.in [ 203 ] 39. A proton and an -particle accelerated through same voltage. The ratio of their De- broglie wavelength will be : (1) 1 : 2 (2) 2 2 :1 (3) 2 :1 (4) 2 : 1 40. The De Broglie wavelength of an atom at absolute temperature T K will be - (1) h mKT (2) h 3mKT (3) 3mKT h (4) 3mKT 41. The De-Broglie wavelength associated with electrons revolving round the nucleus in a hydrogen atom in ground state, will be- (1) 0.3 Å (2) 3.3 Å (3) 6.62 Å (4) 10 Å 42. The wavelength of very fast moving electron (v  c) is : (1) 0 h m v = (2) h 2mE  = (3) 2 2 h 2mE  = (4) 2 2 0 v h 1 c m v −  = 43. Which experiment explains the wave nature of electron :- (1) Michelson's experiment (2) Davisson Germer experiment (3) Roentgen experiment (4) Rutherford experiment 44. In davisson-Germer experiment, the filament emits :- (1) Photons (2) Protons (3) X - rays (4) Electrons 45. The correct curve between intensity of scattering (I) and the angle of diffraction  in Davisson - Germer experiment is : (1) I  50° (2) I  50° (3) I  50° (4) I  50° 46. In Davisson - Germer experiment, Nickel crystal acts as :- (1) Perfect reflector (2) Three dimensional diffraction grating (3) Ideal absorber (4) Two dimensional diffraction grating 47. The diffracted waves in the Davisson-Germer experiment are :- (1) Electrons (2) X - Rays (3) Photons (4) Protons 48. An electron and a proton have the same De-Broglie wavelength. Then the kinetic energy of the electron is : (1) zero (2) Infinity (3) Equal to kinetic energy of proton (4) Greater than the kinetic energy of proton 49. De Broglie equation for an electron shows is : (1) Particle nature (2) Wave nature (3) Dual nature (4) None of these 50. What will happen to De Broglie's wavelength if the velocity of electron is increased : (1) It will increase (2) It will decrease (3) It will remain same (4) It will become twice 51. A photon of wavelength 4400Å is passing through vaccum. The effective mass and momentum of the photon are respectively (1) 5 × 10–36 kg, 1.5 × 10–27 kg – m/s (2) 5 × 10–35 kg, 1.5 × 10–26 kg – m/s (3) zero, 1.5 × 10–26 kg – m/s (4) 5 × 10–36 kg, 1.67 × 10–43 kg – m/s 52. Which of the following is true for photon :- (1) hc E =  (2) 1 2 E mv 2 = (3) E P 2V = (4) 1 2 E mc 2 = 53. For a moving particle having kinetic energy E, the correct de Broglie wavelength is : (1) It is not applicable for a particle (2) h 2mE (3) h E 2m (4) h 2mE