ch17 - CHAPTER 17 WaveParticle Duality and Quantum Physics...

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CHAPTER 17 Wave–Particle Duality and Quantum Physics 1* · The quantized character of electromagnetic radiation is revealed by ( a ) the Young double-slit experiment. ( b ) diffraction of light by a small aperture. ( c ) the photoelectric effect. ( d ) the J.J. Thomson cathode-ray experiment. ( c ) 2 ·· Two monochromatic light sources, A and B, emit the same number of photons per second. The wavelength of A is l A = 400 nm, and that of B is l B = 600 nm. The power radiated by source B is ( a ) equal to that of source A. ( b ) less than that of source A. ( c ) greater than that of source A. ( d ) cannot be compared to that from source A using the available data. ( b ) 3 · Find the photon energy in joules and in electron volts for an electromagnetic wave of frequency ( a ) 100MHz in the FM radio band, and ( b ) 900 kHz in the AM radio band. ( a ) E = hf ; h = 6.626 × 10 -34 J . s = 4.136 × 10 -15 eV . s ( b ) E = hf E = 6.63 × 10 -26 J = 4.14 × 10 -7 eV E = 5.96 × 10 -28 J = 3.72 × 10 -9 eV 4 · An 80-kW FM transmitter operates at a frequency of 101.1 MHZ. How many photons per second are emitted by the transmitter? P = Nhf ; N = P / hf N = 8 × 10 4 /(6.63 × 10 -34 × 101.1 × 10 6 ) s -1 = 1.19 × 10 30 s -1 5* · What are the frequencies of photons having the following energies? ( a ) 1 eV, ( b ) 1 keV, and ( c ) 1 MeV. ( a ) f = 1/4.14 × 10 -15 Hz = 2.42 × 10 14 Hz. ( b ) f = 2.24 × 10 17 Hz. ( c ) f = 2.24 × 10 20 Hz. 6 · Find the photon energy for light of wavelength ( a ) 450 nm, ( b ) 550 nm, and ( c ) 650 nm. ( a ), ( b ), ( c ) E = hc / l = (1240 eV . nm)/ l ( a ) E = 2.76 eV ( b ) E = 2.25 eV ( c ) E = 1.91 eV 7 · Find the photon energy if the wavelength is ( a ) 0.1 nm (about 1 atomic diameter), and ( b ) 1 fm (1 fm = 10 -15 m, about 1 nuclear diameter). ( a ) E = 1240/0.1 eV = 12.4 keV. ( b ) E = 1240/10 -6 eV = 1.24 GeV.
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Chapter 17 Wave–Particle Duality and Quantum Physics 8 ·· The wavelength of light emitted by a 3-mW He-Ne laser is 632 nm. If the diameter of the laser beam is 1.0 mm, what is the density of photons in the beam? 1. Find the number of photons emitted per second 2. Find the volume containing the photons 3. Density of photons = N / V N = P / E = (3 × 10 -3 /1.6 × 10 -19 )/(1240/632) = 9.56 × 10 15 V = Ac = ( p × 10 -6 /4) × 3 × 10 8 m 3 = 2.36 × 10 2 m 3 r = 9.56 × 10 15 /2.36 × 10 2 m -3 = 4.05 × 10 13 m -3 9* · True or false: In the photoelectric effect, ( a ) the current is proportional to the intensity of the incident light. ( b ) the work function of a metal depends on the frequency of the incident light. ( c ) the maximum kinetic energy of electrons emitted varies linearly with the frequency of the incident light. ( d ) the energy of a photon is proportional to its frequency. ( a
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This note was uploaded on 01/23/2011 for the course PHYS 122 taught by Professor Cramer during the Winter '08 term at University of Washington.

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ch17 - CHAPTER 17 WaveParticle Duality and Quantum Physics...

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