Chapter 40: Answers to Stop to Think Questions and Odd-Numbered Exercises and Problems

Stop to Think Questions

  1. 1. vA=vB>vC. The de Broglie wavelength is λ=h/mv, so slower particles have longer wavelengths. The wave amplitude is not relevant.

  2. 2. c. The n=2 state has a node in the middle of the box. The antinodes are centered in the left and right halves of the box.

  3. 3. n=5. There are five antinodes and four nodes (excluding the ends).

  4. 4. d. The wave function reaches zero abruptly on the right, indicating an infinitely high potential-energy wall. The exponential decay on the left shows that the left wall of the potential energy is not infinitely high. The node spacing and the amplitude increase steadily in going from right to left, indicating a steadily decreasing kinetic energy and thus a steadily increasing potential energy.

  5. 5. c. E=(n−12)ℏω, so 52ℏω is the energy of the n=3 state. An n=3 state has 3 antinodes.

  6. 6. b. The probability of tunneling through the barrier increases as the difference between E and U0 decreases. If the tunneling probability increases, the reflection probability must decrease.

Exercises and Problems

  1. 1.

    1. Infrared

    2. 1.5 nm

  2. 3. 21 eV

  3. 5. 17 eV

  4. 9.

    1. 0.159 nm

    2. 0.195 nm

    3. 0.275 nm

  5. 11. 2.3 pm

  6. 13.

    The graph illustrates the wavefunction for a potential well drawn on a graph.
  7. 15.

  8. 17.

    1. 0.49 eV, 1.5 eV, 2.4 eV

    2. 640 nm

  9. 19. 1.4 N/m

  10. 21. 519 nm

  11. 25. 0.0095%

  12. 27.

    1. 250,000,000

  13. 29.

    1. 37.7 eV, 151 eV, 339 eV, 603 eV

    2. 11.0 nm, 4.12 nm, 6.59 nm, 2.20 nm, 2.75 nm, 4.71 nm

    3. Ultraviolet

  14. 33.

    The figure consists of two parts that illustrate the probability density for a particle in a rigid box for three states.
    n= 1 2 3
    b. Most likely 12L 14L, 34L 16L, 36L, 56L
    c. Least likely 0, L 0, 12L, L 0, 13L, 23L, L
    d. Prob in left 13 from graph <13 >13 13
    e. Prob in left 13 calculated 0.195 0.402 0.333
  15. 35. 10%

  16. 37.

    1. 0.15 nm

    2. One atomic diameter

  17. 39.

    1. A1=1(πb2)1/4

    2. Prob(x<−b or x>b)=2πb2∫b∞e−x2/b2dx

    3. 15.7%

  18. 41.

  19. 43. 14of the radius

  20. 45. 0.012

  21. 47. 9.7%

  22. 49. 10−1.17×1032