The Scientific Evidence

Answer any three (3) of the below questions, each with a brief paragraph describing either an experiment and the interpretation of its results or a theoretical argument. If you do not recall the name associated with the experiment or argument you have in mind, a brief description will suffice. Although sometimes there will be more than one correct answer, you need give only one.

1. How do we know that electrons sometimes can be described by Newtonian trajectories determined by F=ma?

2. How do we know photons carry momentum?

3. How do we know that there is a wavelength associated with electrons, , where p is is their momentum?

4. How do we know that the probability of the arrival of photons is determined by , the square of the amplitude of the electromagnetic field?

5. Why it is impossible to balance a pencil on its end for more than several seconds without ``cheating''?

6. In a hydrogen atom, what prevents the fall of the electron into the proton?