This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Chapter 38 p. 1 CHAPTER 38 Early Quantum Theory and Models of the Atom Note: At the atomic scale, it is most convenient to have energies in electronvolts and wavelengths in nanometers. A useful expression for the energy of a photon in terms of its wavelength is E = hf = hc / = (6.63 10 34 J s)(3.00 10 8 m/s)(10 9 nm/m) /(1.60 10 19 J/eV) ; E = (1.24 10 3 eV nm)/ . 1. We find the temperature for a peak wavelength of 440 nm: T = (2.90 10 3 m K)/ P = (2.90 10 3 m K)/(440 10 9 m) = 6.59 10 3 K . 2. ( a ) The temperature for a peak wavelength of 25.0 nm is T = (2.90 10 3 m K)/ P = (2.90 10 3 m K)/(25.0 10 9 m) = 1.16 10 5 K . ( b ) We find the peak wavelength from P = (2.90 10 3 m K)/ T = (2.90 10 3 m K)/(2800 K) = 1.04 10 6 m = 1.04 m . Note that this is not in the visible range. 3. Because the energy is quantized, E = nhf , the difference in energy between adjacent levels is ? E = hf = (6.63 10 34 J s)(8.1 10 13 Hz) = 5.4 10 20 J = 0.34 eV . 4. ( a ) We find the peak wavelength from P = (2.90 10 3 m K)/ T = (2.90 10 3 m K)/(273 K) = 1.06 10 5 m = 10.6 m . This wavelength is in the infrared . ( b ) We find the peak wavelength from P = (2.90 10 3 m K)/ T = (2.90 10 3 m K)/(3300 K) = 8.79 10 7 m = 879 nm . This wavelength is in the near infrared . ( c ) We find the peak wavelength from P = (2.90 10 3 m K)/ T = (2.90 10 3 m K)/(4 K) = 7.25 10 4 m = 0.73 mm . This wavelength is in the far infrared . 5. ( a ) The potential energy on the first step is U 1 = mgh = (58.0 kg)(9.80 m/s 2 )(0.200 m) = 114 J . ( b ) The potential energy on the second step is U 2 = mg 2 h = 2 U 1 = 2(114 J) = 228 J . ( c ) The potential energy on the third step is U 3 = mg 3 h = 3 U 1 = 3(114 J) = 342 J . ( d ) The potential energy on the n th step is U n = mgnh = nU 1 = n (114 J) = 114 n J . ( e ) The change in energy is ? E = U 2 U 6 = (2 6)(114 J) = 456 J ....
View
Full
Document
 Spring '08
 ROSS
 Energy, Photon

Click to edit the document details