Review Questions: Modern Physics
Answers
A. electrons.
B. protons.
C. neutrons.
D. all of these.
E. none of these
2. Reflection occurs when outer electrons of atoms are shaken in their shells. Glowing occurs when outer electrons of atoms are shaken
A. at a higher frequency.
B. at a higher amplitude.
C. out of their shells and in again.
D. none of these.
3. To say that energy levels in an atom are discrete is to say the energy levels are well defined and
A. separate from one another.
B. separated from one another by the same energy increments.
C. continuous.
D. private.
4. An excited atom is an atom
A. that has excess vibration.
B. that has one or more displaced electrons.
C. with more protons than electrons.
D. that is frantic.
5. Light is emitted when an electron
A. is boosted to a higher energy level.
B. makes a transition to a lower energy level.
C. neither of these.
6. An atom that absorbs a photon of a certain energy can then emit
A. only a photon of that energy.
B. a photon of any energy.
C. only a photon of the same or higher energy.
D. only a photon of the same or lower energy.
7. The energy of a photon is related to
A. the energy given to the atom that emits it.
B. the energy level difference though which it falls.
C. its frequency.
D. all of these.
E. none of these.
8. The highest frequency light of those below is
A. red.
B. green.
C. blue.
D. violet.
E. all the same.
9. Which color of light carries the most energy per photon?
A. red
B. green
C. blue
D. violet
E. all the same
10. Ultraviolet light is
A. more energetic than X-rays.
B. produced by crossed Polaroids.
C. electromagnetic energy.
D. present everywhere.
E. none of these.
11. Compared to the energy of a photon of red light, the energy of a photon of blue light is
A. less.
B. more.
C. the same.
12. The variety of colors seen in a burning log come from the variety of
A. multi-layered incandescent surfaces.
B. electron transitions in various atoms.
C. temperatures.
D. chemicals in the log.
E. absorbing gases between the log and the viewer.
13. Fluorescent minerals on display in museums are illuminated with
A. infrared light.
B. ultraviolet light.
C. often either or both.
D. none of these.
14. The greater proportion of energy immediately converted to heat rather than light occurs in
A. a fluorescent lamp.
B. an incandescent lamp.
C. both the same.
15. A photographer wishes to use a safety light in the darkroom that will emit low-energy photons. The best visible color to use is
A. violet.
B. blue.
C. green.
D. actually any of these.
E. none of these.
Reasoning: All these photons have too much
energy which results in exposing the film.
16. An atom that emits a certain frequency of light is
A. not likely to absorb that same frequency.
B. an absorber of the same frequency.
17. The white light emitted by a fluorescent lamp is provided by the
A. mercury vapor in the lamp.
B. phosphors on the inner surface of the lamp.
C. high temperature of the glowing gas.
D. filtering effect of the glass tubing.
18. The main visible difference between phosphorescent and fluorescent materials is
A. an afterglow.
B. a difference in brightness.
C. the greenish color of phosphorescence.
19. Which light source is more energy-efficient?
A. a fluorescent lamp
B. an incandescent lamp
C. both about the same
20. Some minerals glow when illuminated with ultraviolet light. This is because
A. ultraviolet photons kick atomic electrons in the mineral into higher energy states.
B. ultraviolet photons have such high energy.
C. of selective reflection.
D. of selective transmission.
E. none of these.
21. Some light switches glow in the dark after the lights are turned off. This is because of
A. fluorescence.
B. phosphoresence.
C. incandescence.
D. a time delay between excitation and de-excitation.
E. none of these.
Reasoning: In phosphorescent materials,
the excited states have a much longer lifetime than usual (i.e. more than 10-8
seconds).
22. A hydrogen atom is in its ground state when the electron
A.is at the center of the atom.
B. has been ionized.
C. is in the innermost orbit.
D. has absorbed a photon.
23. According to Neils Bohr, an electron in an excited state could give off
A. at most a single photon until the atom was excited again.
B. several photons in a series of transitions to the ground state.
C. a continuous cascade of photons for a high-level transition.
D. none of these.
24. The Bohr model of the atom is akin to a
A. miniature solar system.
B. blob of plum pudding, where raisins represent atomic nuclei.
C. central heavy ball with lighter balls connected by springs.
D. all of these.
25. We now consider the Bohr model of the atom to be
A. an accurate picture of a hydrogen atom.
B. totally useless - of historical interest only.
C. defective and oversimplified, but still useful.