State what the term photon means.
Electromagnetic radiation with frequency f that varies and intensity I that stays constant is directed at a metal surface. For some frequencies, electrons are emitted from the metal surface. The way in which the maximum kinetic energy E_{\text{MAX}} of the emitted electrons varies with f is shown in Fig. 7.1.
State the phenomenon’s name.
Describe three conclusions that can be obtained from the graph in Fig. 7.1. The conclusions may be qualitative or quantitative.
The experiment in (b) is repeated twice, and one change is made each time. State, with a reason, how the graph obtained would compare with Fig. 7.1 when:
a different metal is used, while the intensity $I$ of the radiation stays the same
the same metal is used, but the electromagnetic radiation has intensity $2I$.