Physics 202 MWF 10:20 Spring 2003 (Ford)
Exam IV Chapts. 27, 29, 30 in Cutnell and Johnson 5e
Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.
(14 pts) 1. Use the Bohr model to calculate the de Broglie wavelength of an electron in the state of the hydrogen atom that has energy -13.6 eV.
Ans. ___3.32 × 10-10 m____
(14 pts) 2. In the Lyman series of spectral lines in emission from the hydrogen atom, the final state of the atom after emission occurs is the ground state.
a) Calculate the longest wavelength in the Lyman series.
Ans. ____122 nm___
b) The ground state energy of the hydrogen atom is -13.6 eV. What is the energy of the initial state for the transition that gives the longest wavelength in the Lyman series?
Ans. ____-3.4 eV___
(18 pts) 3. Coherent light with wavelength 600 nm passes through a narrow silt and the diffraction pattern is observed on a screen 3.00 m from the slit. The width of the central diffraction maximum is observed to be 4.00 mm. What is the width of the slit?
Ans. _____0.900 mm____
(18 pts) 4.
a) A photon has momentum 9.46 × 10-28 kg·m/s. What are the energy and wavelength of this photon?
Ans. energy ___2.84 × 10-19 J = 1.77 eV____
wavelength _____700 nm____
b) An electron (mass 9.11 × 10-31 kg) has momentum 9.46 × 10-28 kg·m/s. What are the energy and de Broglie wavelength of this electron?
Ans. energy ___4.91 × 10-25 J = 3.07 × 10-6 eV_____
de Broglie wavelength ____700 nm____
(18 pts) 5. The longest wavelength of light that produces photoelectrons from a certain metal surface is 500 nm. What is the maximum kinetic energy of the emitted photoelectrons when light of wavelength 400 nm falls on this surface?
Ans. ___9.9 × 10-20 J = 0.62 eV__________
(18 pts) 6. Two coherent sources A and B of radio waves are 5.0 m apart. Each source emits waves with wavelength 6.0 m. Consider points along the line between the sources. At what distances x from source A do you get the following kinds of interference? (Note: In each case there might be more than one distance. If so, you must give all of them?
a) constructive
Ans. ____2.5 m______
b) destructive
Ans. ___1.0 m, 4.0 m___