MasteringPhysics: Print View with Answers 1 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... Signed in as Weida Wu , Instructor Rutgers Analytical Physics 750:228, Spring 2016 My Courses Help Sign Out ( RUPHY228S16 ) Course Settings University Physics with Modern Physics, 14e Young/Freedman Instructor Resources Course Home eText Study Area Assignments Roster Gradebook Item Library 7. Photons, Electrons, Matter Waves, and Atoms Overview Summary View Diagnostics View [ Edit ] Print View with Answers 7. Photons, Electrons, Matter Waves, and Atoms Due: 11:59pm on Sunday, March 20, 2016 To understand how points are awarded, read the Grading Policy for this assignment. Does the Photoelectric Effect Depend on the Properties of the Incident Light? Description: Short conceptual problem on the effect of increasing light intensity and frequency in an experiment on photoelectric effect. Based on Young/Geller Conceptual Analysis 28.1. Light striking a metal surface causes electrons to be emitted from the metal via the photoelectric effect. Part A In a particular experiment to study the photoelectric effect, the frequency of the incident light and the temperature of the metal are held constant. Assuming that the light incident on the metal surface causes electrons to be ejected from the metal, what happens if the intensity of the incident light is increased? Check all that apply. Hint 1. How to approach the problem In the photoelectric effect, some an incident photon's energy is used to remove an electron from the metal, while the remainder becomes the electron's kinetic energy. The energy required to remove the electron from the metal is called the work function of the metal, and it is a constant for a given material. The stopping potential is the electric potential needed for an electron at rest to have as much electric potential energy as the kinetic energy of the electron ejected from the metal. The stopping potential can be measured directly from the experiment. If the intensity of the incident light is increased, but its frequency is kept constant, the number of photons striking the metal per unit time increases, but the energy of individual incident photons remains constant. How does this affect the kinetic energy of the emitted electrons and their number per unit time? Hint 2. Find the kinetic energy of the emitted electrons In the photoelectric effect, some of the incident photon's energy is used to remove an electron from the metal, while the remainder becomes the electron's kinetic energy . If the frequency of the incident photon is , and the work function of the metal is , which of the following expressions gives the maximum kinetic energy of the emitted electron, ? In these expressions is Planck's constant. Hint 1. Energy of a photon The energy of a photon of frequency is given by , where is Planck's constant. Hint 2. Work function Recall that the work function of a metal is the energy required to remove an electron from that metal. ANSWER: As you found out, the maximum kinetic energy of the emitted electron does not depend on the intensity of the incident light. If the intensity of the incident light is varied, how does this affect the maximum speed of the emitted electron? ANSWER: 4/22/2016 12:18 AM MasteringPhysics: Print View with Answers 2 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... The work function of the metal decreases. The number of electrons emitted from the metal per second increases. The maximum speed of the emitted electrons increases. The stopping potential increases. When the intensity of the incident light is increased, while its frequency is held constant, more photons will hit the metal per unit time and a larger number of electrons will be emitted per unit time. Experimentally, this corresponds to higher maximum currents observed between the anode and cathode. Part B In another experiment, the intensity of the incident light and the temperature of the metal are held constant. Assuming that the initial light incident on the metal surface causes electrons to be ejected from the metal, what happens if the frequency of the incident light is increased? Check all that apply. Hint 1. How to approach the problem In the photoelectric effect, some of the incident photon's energy is used to remove an electron from the metal, while the remainder becomes the electron's kinetic energy. Therefore, if the photon's energy increases, so does the electron's kinetic energy because the energy required to remove an electron from the metal (the work function) is a constant for any given material. Also, recall that the stopping potential can be used as an indirect measurement of the maximum kinetic energy of the emitted electrons. Thus, if the electron's energy increases, the stopping potential increases as well. ANSWER: The work function of the metal increases. The number of electrons emitted from the metal per second increases. The maximum speed of the emitted electrons increases. The stopping potential increases. Alternative Exercise 38.52 Description: A hydrogen atom undergoes a transition from the n =5 to the n = 2 state. (a) What is the wavelength of the photon that is emitted? (b) What is the energy of this photon. (c) If the angular momentum is conserved and if the Bohr model is used to... A hydrogen atom undergoes a transition from the 5 to the 2 state. Part A What is the wavelength of the photon that is emitted? ANSWER: = 434 Part B What is the energy of this photon. ANSWER: = 2.86 Part C If the angular momentum is conserved and if the Bohr model is used to describe the atom, what must the angular momentum be of the photon that is emitted? ANSWER: = 3.17×10−34 Exercise 38.9 Description: When ultraviolet light with a wavelength of ## nm falls on a certain metal surface, the maximum kinetic energy of the emitted photoelectrons is measured to be ## eV. (a) What is the maximum kinetic energy of the photoelectrons when light of... When ultraviolet light with a wavelength of 400.0 Typesetting math: falls on a certain metal surface, the maximum kinetic energy of the emitted photoelectrons is measured to be 1.10 . 4/22/2016 12:18 AM MasteringPhysics: Print View with Answers 3 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... Part A What is the maximum kinetic energy of the photoelectrons when light of wavelength 285.0 falls on the same surface? ANSWER: = 2.35 = Exercise 38.16 Description: X rays are produced in a tube operating at ## kV. After emerging from the tube, x rays with the minimum wavelength produced strike a target and undergo Compton scattering through an angle of 45.0 degree(s). (a) What is the original x-ray... rays are produced in a tube operating at 21.0 scattering through an angle of . . After emerging from the tube, rays with the minimum wavelength produced strike a target and undergo Compton Part A What is the original -ray wavelength? Express your answer with the appropriate units. ANSWER: = 59.2 = Part B What is the wavelength of the scattered rays? Express your answer with the appropriate units. ANSWER: = 59.9 = Part C What is the energy of the scattered rays? ANSWER: = 20.7 = Exercise 38.5 Description: A photon has momentum of magnitude p. (a) What is the energy of this photon? Give your answer in joules. (b) What is the energy of this photon? Give your answer in electron volts. (c) What is the wavelength of this photon? (d) In what region of ... A photon has momentum of magnitude . Part A What is the energy of this photon? Give your answer in joules. ANSWER: = = 2.45×10−19 Part B What is the energy of this photon? Give your answer in electron volts. ANSWER: Typesetting math: 4/22/2016 12:18 AM MasteringPhysics: Print View with Answers 4 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... = 1.53 = Part C What is the wavelength of this photon? ANSWER: = 8.11×10−7 = Part D In what region of the electromagnetic spectrum does it lie? ANSWER: gamma rays radio waves infrared ultraviolet visible light Exercise 38.6 Description: The photoelectric threshold wavelength of a tungsten surface is 272 nm. (a) Calculate the maximum kinetic energy of the electrons ejected from this tungsten surface by ultraviolet radiation of frequency 1.45 * 10^15 (Hz). Express the answer in... The photoelectric threshold wavelength of a tungsten surface is 272 . Part A Calculate the maximum kinetic energy of the electrons ejected from this tungsten surface by ultraviolet radiation of frequency electron volts. . Express the answer in ANSWER: = 1.44 Problem 38.21 Description: (a) An electron inside a hydrogen atom is confined to within a space of 0.110 nm. What is the minimum uncertainty in the electron's velocity? (hbar = 1.055 * 10^-34 (J * s), m_el = 9.11 * 10^-31 (kg))... Part A An electron inside a hydrogen atom is confined to within a space of 0.110 nm. What is the minimum uncertainty in the electron's velocity? ( ) , ANSWER: 5.26 × 105 m/s 7.50 × 105 m/s 5.26 × 107 m/s 5.26 × 109 m/s 7.50 × 107 m/s Exercise 38.13 Description: Protons are accelerated from rest by a potential difference of DeltaV and strike a metal target. (a) If a proton produces one photon on impact, what is the minimum wavelength of the resulting x rays? (b) Find the minimum wavelength if ##-keV... Typesetting math: 4/22/2016 12:18 AM MasteringPhysics: Print View with Answers 5 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... Protons are accelerated from rest by a potential difference of 4.50 and strike a metal target. Part A If a proton produces one photon on impact, what is the minimum wavelength of the resulting x rays? ANSWER: = 2.76×10−10 = Part B Find the minimum wavelength if 4.50- electrons are used instead? ANSWER: = 2.76×10−10 = Part C Why do x-ray tubes use electrons rather than protons to produce x rays? ANSWER: 3721 Character(s) remaining Electron beams are much more easily produced and accelerated than proton beams. Exercise 38.14 Description: (a) What is the minimum potential difference between the filament and the target of an x-ray tube if the tube is to produce x-rays with a wavelength of lambda? (b) What is the shortest wavelength produced in an x-ray tube operated at a voltage... Part A What is the minimum potential difference between the filament and the target of an x-ray tube if the tube is to produce x-rays with a wavelength of 0.160 ? ANSWER: = = 7760 Also accepted: = 7760, = 7750, h*2.998*10^8/(lambda*1.60*10^-19) = 7760, = 7760 Part B What is the shortest wavelength produced in an -ray tube operated at a voltage of 35.0 ? ANSWER: = h*c/(V*e)*10^9 = 3.55×10−2 Also accepted: h*c/(V*1.60*10^-19)*10^9 = 3.55×10−2, h*2.998*10^8/(V*e)*10^9 = 3.54×10−2, h*2.998*10^8/(V*1.60*10^-19)*10^9 = 3.55×10−2, h*c/(V*e)*10^9 = 3.55×10−2 Exercise 38.18 Description: A photon with wavelength lambda scatters from an electron that is initially at rest. (a) What must be the angle between the direction of propagation of the incident and scattered photons if the speed of the electron immediately after the... A photon with wavelength 0.1375 scatters from an electron that is initially at rest. Part A Typesetting math: 4/22/2016 12:18 AM MasteringPhysics: Print View with Answers 6 of 6 https://session.masteringphysics.com/myct/assignmentPrintView?assign... What must be the angle between the direction of propagation of the incident and scattered photons if the speed of the electron immediately after the collision is ? ANSWER: = acos(1-3.00*10^8*(lambda*9.11/10^31*v)^2/6.626*10^34/(2*6.626/10^34*3.00*10^8-lambda*9.11/10^31*v^2)) = 99.6 Also accepted: acos(1-2.998*10^8*(lambda*9.108/10^31*v)^2/6.626*10^34/(2*6.626/10^34*2.998*10^8-lambda*9.108/10^31*v^2)) = 99.6, acos(1-3.0*10^8* (lambda*9.108/10^31*v)^2/6.626*10^34/(2*6.626/10^34*3.0*10^8-lambda*9.108/10^31*v^2)) = 99.6, acos(1-2.998*10^8*(lambda*9.11/10^31*v)^2/6.626*10^34 /(2*6.626/10^34*2.998*10^8-lambda*9.11/10^31*v^2)) = 99.6, acos(1-3.00*10^8*(lambda*9.11/10^31*v)^2/6.626*10^34/(2*6.626/10^34*3.00*10^8-lambda*9.11 /10^31*v^2)) = 99.6 Copyright © 2016 Pearson. All rights reserved. Legal Notice Privacy Policy Permissions Support Typesetting math: 4/22/2016 12:18 AM

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