The Photoelectric Effect Practice Test

A student shines red light of very high intensity on a metal surface and observes no photoelectrons. Switching to dim blue light causes immediate emission of electrons. The student keeps the metal and setup unchanged. Which reasoning best accounts for the change?

Two trials use the same metal. Trial 1: light at frequency just above threshold produces electrons with low maximum kinetic energy. Trial 2: frequency is unchanged but intensity is tripled, producing three times as many electrons per second with the same maximum kinetic energy. Which statement best accounts for this result?