Section 1
Questions
In the photoelectric experiments, the current (number of electrons emitted per unit time) is proportional to the intensity of light. Can this result alone be used to distinguish between the classical and auantum theories?
In Figure $2-2$ why does the photoelectric current not rise vertically to its maximum (saturation) value when the applied potential difference is slightly more positive than $-V_{0} ?$
Why is it that even for incident radiation that is monochromatic, photoelectrons are emitted with a spread of velocities?
The existence of a cutoff frequency in the photoelectric effect is often regarded as the most potent objection to a wa ve theory. Explain.
Why are photoelectric measurements very sensitive to the nature of the photoelectric surface?
Do the results of photoelectric experiments invalidate Young's interference experiment?
Can you use the device of letting $h \rightarrow 0$ to obtain classical results from quantum results in the case of the photoelectric effect? Explain.
Assume that the emission of photons from a source of radiation is random in direction. Would you expect the intensity (or energy density) to vary inversely as the square of the distance from the source in the photon theory as it does in the wave theory?
Does a photon of energy $E$ have mass? If so, evaluate it.
Why, in Compton scattering, would you expect $\Delta \lambda$ to be independent of the materials of which the scatterer is composed?
Would you expect to observe the Compton effect more readily with scattering targets composed of atoms with high atomic number or those composed of atoms with low atomic number? Explain.
Do vou obserye a Compton effect with visible light? Whv?
Would you expect a definite minimum wavelength in the emitted radiation for a given value of the energy of an electron incident on the target of an x-ray tube from the classical electromagnetic theory of the process?
Does a television tube emit $x$ rays? Explain.
What effect(s) does decreasing the voltage across an x-ray tube have on the resulting x-ray spectrum?
Discuss the bremsstrahlung process as the inverse of the Compton process. Of the photoelectric process.
Describe several methods that can be used to determine experimentally the value of Planck's constant $h$.
From what factors would you expect to judge whether a photon will lose its energy in interactions with matter by the photoelectric process, the Compton process, or the pair production process?
Can you think of experimental evidence contradicting the idea that vacuum is a sea of electrons in negative energy states?
Can electron-positron annihilation occur with the creation of one photon if a nearby nucleus is available for recoil momentum?
Explain how pair annihilation with the creation of three photons is possible. Is it possible in principle to create even more than three photons in a single annihilation process?
What would be the inverse of the process in which two photons are created in electronpositron annihilation? Can it occur? Is it likely to occur?
What is wrong with taking the geometrical interpretation of a cross section as literally true?