Physics 10 Homework SolutionsChapter 31

(1) Planck modeled the atoms in the cavity walls as harmonic oscillators. He assumedthat these oscillators could only absorb or radiate electromagnetic radiation in certainamounts of energy. This energy was proportional to the frequency of the radiation.Thus, Planck quantized the atoms and not the radiation field.

(2) The energy carried by light is proportional to its frequency. Since red light haslower frequency than blue light, red light carries less energy than blue light. Sinceradio waves have lower frequency than X-rays, radio waves carry less energy than X-rays.

(3) Higher energy photons will deliver more energy to an electron than lower energyphotons. Red light photons lower frequency and, thus, less energy than violet lightphotons. No matter how many red light photons are present, they can deliver no moreenergy to a single electron than they have to give. Thus, the violet light photons, withgreater energy, will deliver more energy to an electron.

(4) When electrons passing through two-slits arrive at the screen, they arrive asparticles. The electrons strike photographic emulsion, and this process shows whereindividual electrons strike the photographic plate. However, the distribution of thepattern on the photographic plate shows a wave-like interference.

(5) It is the energy of an incident photon that is transferred as kinetic energy to anelectron in the photoelectric effect. Since a photon’s energy is proportional to itsfrequency, increasing the frequency of a photon will increase the kinetic energy of theelectron it strikes. The brightness of light hitting a metallic surface is a measure of thenumber of photons striking the surface. Thus, brighter light will eject more electrons.

(6) The wavelength of a particle is inversely proportional to the momentum of theparticle. If two particles have identical speeds, the more massive particle will have thelarger momentum. Thus, the more massive particle, the proton, will have the smallerwavelength.