Modern Physics for Scientists and Engineers
4th Edition
ISBN: 9781133103721
Author: Stephen T. Thornton, Andrew Rex
Publisher: Cengage Learning
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Chapter 3, Problem 2Q
To determine
If it matters that the electron in the
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In a laboratory experiment designed to duplicate Thomson’s determination of qe / me , a beam of electrons having a velocity of 6.00×107 m/s enters a 5.00×10−3 T magnetic field. The beam moves perpendicular to the field ina path having a 6.80-cm radius of curvature. Determine qe / me from these observations, and compare the result with the known value.
J. J. Thomson is best known for his discoveries about the
nature of cathode rays. His other important contribution
was the invention, together with one of his students, of
the mass spectrometer, a device that measures the ratio
of mass m to (positive) charge q of an ion.
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An electron entering Thomson’s e/m apparatus has an initial velocity (in horizontal direction only) of 4.0 x 106 m/s. In the lab is a permanent horseshoe magnet of strength 12 mT, which you would like to use. (a) What electric fi eld will you need in order to produce zero defl ection of the electrons as they travel through the apparatus? (b) The length of nonzero E and B fi elds is 2.0 cm. When the magnetic fi eld is turned off, but the same electric field remains, how far in the vertical direction will the electron beam be deflected over this length?magnetic fi eld is turned off, but the same electric fi eld remains, how far in the vertical direction will the electron beam be defl ected over this length
Chapter 3 Solutions
Modern Physics for Scientists and Engineers
Ch. 3 - Prob. 1QCh. 3 - Prob. 2QCh. 3 - Prob. 3QCh. 3 - Prob. 4QCh. 3 - Prob. 5QCh. 3 - Prob. 6QCh. 3 - Prob. 7QCh. 3 - Prob. 8QCh. 3 - Prob. 9QCh. 3 - In the experiment of Example 3.2, how could you...
Ch. 3 - Prob. 11QCh. 3 - Prob. 12QCh. 3 - Prob. 13QCh. 3 - Prob. 14QCh. 3 - Prob. 15QCh. 3 - Prob. 16QCh. 3 - Prob. 17QCh. 3 - Prob. 18QCh. 3 - Prob. 19QCh. 3 - Prob. 20QCh. 3 - Prob. 21QCh. 3 - Prob. 22QCh. 3 - Prob. 23QCh. 3 - Prob. 24QCh. 3 - Prob. 25QCh. 3 - Prob. 26QCh. 3 - Prob. 1PCh. 3 - Prob. 2PCh. 3 - Across what potential difference does an electron...Ch. 3 - Prob. 4PCh. 3 - Prob. 5PCh. 3 - Prob. 6PCh. 3 - Prob. 7PCh. 3 - Prob. 8PCh. 3 - Prob. 9PCh. 3 - Prob. 10PCh. 3 - Prob. 11PCh. 3 - Prob. 12PCh. 3 - Prob. 13PCh. 3 - Prob. 14PCh. 3 - Prob. 15PCh. 3 - Prob. 16PCh. 3 - Calculate max for blackbody radiation for (a)...Ch. 3 - Prob. 18PCh. 3 - Prob. 19PCh. 3 - Prob. 20PCh. 3 - White dwarf stars have been observed with a...Ch. 3 - Prob. 22PCh. 3 - Prob. 23PCh. 3 - Prob. 24PCh. 3 - Prob. 25PCh. 3 - Prob. 26PCh. 3 - Prob. 27PCh. 3 - Prob. 32PCh. 3 - Prob. 33PCh. 3 - Prob. 34PCh. 3 - Prob. 35PCh. 3 - Prob. 36PCh. 3 - Prob. 37PCh. 3 - Prob. 38PCh. 3 - Prob. 39PCh. 3 - Prob. 40PCh. 3 - Prob. 41PCh. 3 - Prob. 42PCh. 3 - Prob. 43PCh. 3 - Prob. 44PCh. 3 - Prob. 45PCh. 3 - Prob. 46PCh. 3 - Prob. 47PCh. 3 - Prob. 48PCh. 3 - Prob. 49PCh. 3 - Prob. 50PCh. 3 - Prob. 52PCh. 3 - Prob. 53PCh. 3 - Prob. 54PCh. 3 - Prob. 55PCh. 3 - Prob. 56PCh. 3 - Prob. 57PCh. 3 - Prob. 58PCh. 3 - Prob. 59PCh. 3 - Prob. 60PCh. 3 - Prob. 61PCh. 3 - Prob. 62PCh. 3 - Prob. 63PCh. 3 - Prob. 64PCh. 3 - Prob. 65PCh. 3 - Prob. 66PCh. 3 - Prob. 67PCh. 3 - Prob. 68PCh. 3 - The Fermi Gamma-ray Space Telescope, launched in...Ch. 3 - Prob. 70P
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- What is the kinetic energy of an electron that passes undeviated through perpendicular electric and magnetic fields if E = 2.0 kV/m and B = 8.0 mT? (m=9.1 × 10-31 kg , q=1.6x-19C ) Select one: a. 1.60 eV b. 0.71 eV c. 2.85 eV d. 0.18 eVarrow_forwardIn the Bohr model of the hydrogen atom an e-1 in the ground state has a speed of 2.20×10^6m/s at a radius of 4.29×10^-11m.The charge of an e-1 is 1.60×10^-19c.Find the magnetic dipole moment of the atomarrow_forwardIn Thomson’s e/m experiment, does it matter whether the electron passing through interacts fi rst with the electric fi eld or with the magnetic fi eld or both simultaneously? Explain.arrow_forward
- Electrons passes undeviated through crossed electric and magnetic fields. If E = 5 × 10¹ N/c and B = 4 × 10-4 Wb/m² find the velocity of electrons.arrow_forwardCathode rays are accelerated by a P.D. of 2000 volt and enter the plates of a Thomson tube as a collimated beam. The P.D. between the plates is 800 volt and the plates are separated by a distance of 1 cm. The path of the beam of electrons is normal to the electrical field. Find the magnetic field that must be applied perpendicular to the beam over the electrical field so that the beam is undeviated. e/m = 1.76 × 1011 C/kg. %3Darrow_forwardWhat is the kinetic energy of an electron that passes undeviated through perpendicular electric and magnetic fields if E = 4.0 kV/m and B = 8.0 mT? 0.84 eV 0.65 eV 0.54 eV 1.4 eV 0.71 eVarrow_forward
- In Thomson's experimental setup (Figure given below), the length of the deflecting plate is 3.0 cm and the distance of the screen to the deflecting plate is 1.0m (x axis). With the applied electrical field of 2.1 x10° V/m, image of the electron beam is observed at the height of 36 cm (y axis). With the applied magnetic field of 1.2 x 10³T, the image is seen at the center of the screen with no deflection. c) If the length of the deflecting plate would be 2.5 cm, where would the beam is observed? d) Assuming mass of the electron is known and the value is m,=9.1x1031 kg, find the rest Energy, total energy and the kinetic energy of the electron. e) Find the relativistic momentum of the electron. Hint: Use equations in Thomson's experiment for a, b and c. Use relativistic kinematic equations for d and e by using the velocity you obtained in a. Deflecting plates- Cathode AB Anode Fluorescent screen- High voltage Magnetarrow_forwardElectrons enter a magnetic field traveling at v, = vỹ. The constant, uniform magnetic field B = 0.75 2 T acts as a filter curving the electrons to a small gap that only allows specific electron energies. The source of electrons enters the filter as a beam that is 15 micrometers in diameter and have a range of energies from 5-25 meV. The filter redirects the beam, as pictured, to the right v = và but does not speed them up. If the filter is to further narrow the range of energies from 5-25 meV to 10-12 meV, find the dimensions of the gap. In the picture, calculate ymin and ymer, both of which can be assumed to be equal to the radius of the paths taken within the magnetic field. %3D The beam being focused to 15 um at the start can be assumed to be a point source and take circular paths within the magnetic field. Outgoing "Filtered" Electrons Blocked Electrons -不: Y Vma Incoming Electronsarrow_forwardQ.2 (a) When the cathode-ray tube is placed in a magnetic feld that is directed vertically upwards, the electrons emitted from the cathode follow one of the dashed paths to the face of the tube in Figure 1. Select with explanation, the correct path of the rays. 3 Figure 1. (b) Suppose node fin Figure 2 is connected to ground, and the elements in the circuit have the values & = 12 V, & =4 V, 1= 1=10, R =R, =50 and R; =4 0, find the potentials at points a. b and c, the powerdelivered by e.m.f. source &and the power dissipated in resistors 1, and R.. R1 a Battery Battery 2 R3 Figure 2arrow_forward
- F.j = (-e)(-v,k) × (B,i + B.k) ev Bzj. Solving for B gives F. Br 8.50x10 16 N = 1.13 T. Therefore B = 1.13 Ti – 0.772 Tk. The magnitude o A group of particles is traveling in a magnetic field of unknown magnitude and direction. You observe that a proton moving at 1.70 km/s in the +x-direction experiences a force of 2.10x10-16 N in the +y- direction, and an electron moving at 4.70 km/s in the eve (1.60x10 19 C)(4700 m/s) is B = VB? + B = (1.13 T)² + (-0.772 T)² = 1.37 T. -z-direction experiences a force of 8.50x10-16 N in the +y-direction. Part B For related problem-solving tips and strategies, you may want to view a Video Tutor Solution of Magnetic force on a proton. What is the direction of the magnetic field? (in the xz-plane) Express your answer in degrees. 0 = 60.59 ° from the -z-direction to the +x-direction Submit Previous Answers Request Answer X Incorrect; Try Again; 9 attempts remainingarrow_forwardIn Thomson's experimental setup (Figure given below), the length of the deflecting plate is 3.0 cm and the distance of the screen to the deflecting plate is 1.0m (x axis). With the applied electrical field of 2.1 x10° V/m, image of the electron beam is observed at the height of 36 cm (y axis). With the applied magnetic field of 1.2 x 10° T, the image is seen at the center of the screen with no deflection. a) Find the initial velocity of the electron. b) Find the q/m for the electron. c) If the length of the deflecting plate would be 2.5 cm, where would the beam is observed? d) Assuming mass of the electron is known and the value is m=9.1x1031 kg, find the rest Energy, total energy and the kinetic energy of the electron. e) Find the relativistic momentum of the electron. Hint: Use equations in Thomson's experiment for a, b and c. Use relativistic kinematic equations for d and e by using the velocity you obtained in a. Deflecting plates- Cathode AB Anode Fluorescent screen- High voltage…arrow_forwardif all the energy from a 93 W light bulb ?is emmited on average at 530.0 nm, how many 530.0 nm photons must be emitted each second to account for all 93warrow_forward
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