Chapter 8 Question Set
3. (a) Compare the evidence for the wave nature of light with the evidence for its particle
nature. (b) Why do you think the wave nature of light was established long before its particle
nature?
The properties of interference and diffraction along with agreement with the electromagnetic
theory of light are why light is considered a wave phenomenon. The photoelectric effect and
the discovery of elemental line spectra are evidence of its particle nature. The wave
phenomena were much easier to see and measure than the particle phenomena which
required more extensive technology to discover.
5. Energy is carried in light by means of separate photons, yet not even the faintest light we
can see does not appear as a series of flashes. Explain.
Even very faint light requires a large number of photons traveling at very high speeds. It
requires special conditions to see individual photons striking.
10. The uncertainty principle applies to all bodies, yet its consequences are significant only
for such extremely small particles as electrons, protons, and neutrons. Explain.
The de Broglie waves for larger particles are so relatively small that their wave nature
becomes insignificant. It is only for particles in the atomic range and smaller that the
uncertainty principle and their wave nature become important.
21. (a) What is meant by the ground state of an atom? (b) What is the quantum number of the
ground state of a hydrogen atom in the Bohr model?
The ground state is the state of lowest energy for an atom. The quantum number for
hydrogen is n = 1.
22. What is coherent light? Is the light from a light bulb coherent? The light from the sun?
Coherent light is light that is totally aligned each wave with the next. Coherent light waves
are totally in step. No, the light from a light bulb and the light from the sun are not coherent
light.