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Quantum mechanics exams questions(QUANTUM MECHANICS)

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This just about 20 M.C.Q' S of quantum mechanics which will equip you in your studies

Text of Quantum mechanics exams questions(QUANTUM MECHANICS)

  • 1. The person who reads too much and uses his brain toolittle will fall into lazy habits of thinking.Fuakye Eric GyabengAlbert Einstein

2. PHY 351 MCQS TUTORIALSQUANTUM MECHANICS TUTORIALSPrepared by Prof. F. E. Gyabeng(KNUST)For further infoCall:0207746514/0544295511 [email protected] for slides , questions &others 3. NOTE:Please kindly choose your own answer before looking at thefinal answer.Thank [email protected] 4. 1. Light of a single frequency falls on a photoelectric materialbut no electrons are emitted. Electrons may beemitted if the(A) frequency of light is decreased(B) frequency of light is increased(C) intensity of light is decreased(D) intensity of light is increased(E) velocity of light is increased 5. 1. Light of a single frequency falls on a photoelectric materialbut no electrons are emitted. Electrons may beemitted if the(A) frequency of light is decreased(B) frequency of light is increased(C) intensity of light is decreased(D) intensity of light is increased(E) velocity of light is increased 6. 2. Which of the following types of electromagnetic radiationhas the least energy per photon(A)gamma(B) infrared(C) radio(D) visible(E)X-Rays 7. 2. Which of the following types of electromagnetic radiationhas the least energy per photon(A)gamma(B) infrared(C)radio(D) visible(E)X-Rays 8. 3. An atomic particle of mass m moving at speed v is found tohave wavelength . What is the wavelength of a secondparticle with a speed 3v and the same mass(A) (1/9) ( B) (1/3) (C) (D) 3 (E) 9 9. 3. An atomic particle of mass m moving at speed v is found tohave wavelength . What is the wavelength of a secondparticle with a speed 3v and the same mass(A) (1/9) ( B) (1/3) (C) (D) 3 (E) 9 10. 4. A student performs the photoelectric effect experiment andobtains the data depicted in the accompanying graph ofEkm(max kinetic energy) of photoelectrons vs the frequency of thephotons. What is the approximate work function of thismaterial?(A) 1.5 eV(B) 2.0 eV(C) 2.7 eV(D ) 4.0 eV(E) 6.0 eV 11. 4. A student performs the photoelectric effect experiment andobtains the data depicted in the accompanying graph ofEkm(max kinetic energy) of photoelectrons vs the frequency of thephotons. What is the approximate work function of thismaterial?(A) 1.5 eV(B) 2.0 eV(C) 2.7 eV(D ) 4.0 eV(E) 6.0 eV 12. 5. According to the Bohr theory of the hydrogen atom,electrons starting in the 4th energy level and eventuallyending up in the ground state, could produce a total of howmany lines in the hydrogen spectra?(A) 7(B) 6(C) 5(D) 4(E) 3 13. 5. According to the Bohr theory of the hydrogen atom,electrons starting in the 4th energy level and eventuallyending up in the ground state, could produce a total of howmany lines in the hydrogen spectra?(A) 7(B) 6(C) 5(D) 4(E) 3 14. 6. In Rutherfords famous gold foil scattering experiment, hefound that most alpha particles would pass through the foilundeflected. Which of the following nuclear properties can beinferred from this observation.(A) The nucleus must have a positive charge(B) Most of the mass of an atom is in the nucleus(C) The nucleus contains both protons and neutrons(D) The diameter of the nucleus is small compared to thediameter of the atom(E) none of the above. 15. 6. In Rutherfords famous gold foil scattering experiment, hefound that most alpha particles would pass through the foilundeflected. Which of the following nuclear properties can beinferred from this observation.(A) The nucleus must have a positive charge(B) Most of the mass of an atom is in the nucleus(C) The nucleus contains both protons and neutrons(D) The diameter of the nucleus is small compared to thediameter of the atom(E) none of the above. 16. 7. Which of the following is best explained only by the wavetheory of light(A)blackbody radiation( B) the Compton effect(C) the photoelectric effect(D) pairproduction(E) diffraction 17. 7. Which of the following is best explained only by the wavetheory of light(A)blackbody radiation( B) the Compton effect(C) the photoelectric effect(D) pairproduction(E) diffraction 18. 8. In the photoelectric effect experiment, a stopping potentialof Vstopis needed when light of frequency fo shines on theelectron-emitting metal surface. If the metal surface onwhich the light shines is replaced with a new material thathas half the work function, what is the new stoppingpotential, Vnew for light of frequency shiningon it?(A) V Vnew > 2stop (B) Vnew = 2Vstop (C) V stop < Vnew < 2Vstop (D) Vnew =Vstop (E) It is indeterminate with the given information 19. 8. In the photoelectric effect experiment, a stopping potentialof Vstopis needed when light of frequency fo shines on theelectron-emitting metal surface. If the metal surface onwhich the light shines is replaced with a new material thathas half the work function, what is the new stoppingpotential, Vnew for light of frequency shiningon it?(A) V Vnew > 2stop (B) Vnew = 2Vstop (C) V stop < Vnew < 2Vstop (D) Vnew =Vstop (E) It is indeterminate with the given information 20. 9.The diagram to the below shows the lowest four energylevels for an electron in a hypothetical atom. The electron isexcited to the 1 eV level of the atom and transitions to thelowest energy state by emitting only two photons. Which ofthe following energies could not belong to either of thephotons?(A) 2 eV(B) 4 eV(C) 5 eV(D) 6 eV(E) 9 eV 21. 9.The diagram to the below shows the lowest four energylevels for an electron in a hypothetical atom. The electron isexcited to the 1 eV level of the atom and transitions to thelowest energy state by emitting only two photons. Which ofthe following energies could not belong to either of thephotons?(A) 2 eV(B) 4 eV(C) 5 eV(D) 6 eV(E) 9 eV 22. 10. Monochromatic light falling on the surface of an activemetal causes electrons to be ejected from the metallic surfacewith a maximum kinetic energy of E. What would happen tothe maximum energy of the ejected electrons if the frequencyof the light were doubled?(A) the maximum energy of the electrons would be less than E(B) the maximum energy of the electrons would be E(C) the maximum energy of the electrons would be (2) E(D) the maximum energy of the electrons would be 2E(E) the maximum energy of the electrons would be greaterthan 2E 23. 10. Monochromatic light falling on the surface of an activemetal causes electrons to be ejected from the metallic surfacewith a maximum kinetic energy of E. What would happen tothe maximum energy of the ejected electrons if the frequencyof the light were doubled?(A) the maximum energy of the electrons would be less than E(B) the maximum energy of the electrons would be E(C) the maximum energy of the electrons would be (2) E(D) the maximum energy of the electrons would be 2E(E) the maximum energy of the electrons would be greaterthan 2E 24. 11. If the electrons in an electron microscope are travelingwith a velocity of m/s, what would be theeffective wavelength of the electrons?(A)(B)(C)(D)(E)1.61071.2 10 m 8 6.6 10 m 9 4.5 10 m 11 2.6 10 m 11 8.6 10 m 17 25. 11. If the electrons in an electron microscope are travelingwith a velocity of m/s, what would be theeffective wavelength of the electrons?(A)(B)(C)(D)(E)1.61071.2 10 m 8 6.6 10 m 9 4.5 10 m 11 2.6 10 m 11 8.6 10 m 17 26. 12. A very slow proton has its kinetic energy doubled. Whathappens to the protons corresponding deBroglie wavelength?(A) the wavelength is decreased by a factor of 2(B) the wavelength is halved(C) there is no change in the wavelength(D) the wavelength is increased by a factor of 2(E) the wavelength is doubled. 27. 12. A very slow proton has its kinetic energy doubled. Whathappens to the protons corresponding deBroglie wavelength?(A) the wavelength is decreased by a factor of 2(B) the wavelength is halved(C) there is no change in the wavelength(D) the wavelength is increased by a factor of 2(E) the wavelength is doubled. 28. 13. The diagram shows light being emitted due to a transitionfrom the n=3 to the n=2 level of a hydrogen atom in the Bohrmodel. If the transition were from the n=3 to the n=1 levelinstead, the light emitted would have(A)lower frequency(B) less energy(C) longer wavelength(D) greater speed(E) greater momentum 29. 13. The diagram shows light being emitted due to a transitionfrom the n=3 to the n=2 level of a hydrogen atom in the Bohrmodel. If the transition were from the n=3 to the n=1 levelinstead, the light emitted would have(A)lower frequency(B) less energy(C) longer wavelength(D) greater speed(E) greater momentum 30. 14. Which color of light emitted from an atom would beassociated with the greatest change in energy of the atom?(A)Blue(B) Green(C) Red(D) Violet(E) Yellow 31. 14. Which color of light emitted from an atom would beassociated with the greatest change in energy of the atom?(A)Blue(B) Green(C) Red(D) Violet(E) Yellow 32. Questions 15-16 relate to the photoelectric effect and the fivegraphs below 33. 15. Which graph best shows the maximum kinetic energy K ofthe photoelectrons as a function of the frequency of incidentlight?(A)A(B) B(C) C(D) D(E) E 34. 15. Which graph best shows the maximum kinetic energy K ofthe photoelectrons as a function of the frequency of incidentlight?(A)A(B) B(C) C(D) D(E) E 35. 16. Which graph best shows the maximum kinetic energy K ofa photoelectron as a function of the intensity of incident light?(A)A(B) B(C) C(D) D(E) E 36. 16. Which graph best shows the maximum kinetic energy K ofa photoelectron as a function of the intensity of incident light?(A)A(B) B(C) C(D) D(E) E 37. 17. Electrons that have been accelerated from rest through apotential difference of 150 volts have a de Brogliewavelength of approximately 1 Angstrom ( meter). Inorder to obtain electrons whose de Broglie wavelength is 0.5Angstrom (5 x meter), what accelerating potential isrequired?(A)37.5 V(B)75 V(C)300 V( D)600 V(E)22,500 V10 1011 10 38. 17. Electrons