Modern Physics Ideas

How does the photoelectric effect produce an electric current in a circuit?

When we connect a photosensitive surface (cathode) and a collector (anode) in a circuit with a cell, the ejected electrons are attracted to the collector and so a current flows

Why does increasing the voltage of the collector (anode) not increase the photoelectric current?

Making the collector (anode) more positive does not increase the current as all the ejected electrons are already being attracted across to the collector (anode)

Why does a current still flow in a photoelectric circuit without a battery?

A current still flows even when there is no battery in the circuit because the ejected electrons drift across to the collector (anode)

What happens when the anode is made negative, and what is the cutoff voltage?

Making the collector (anode) negative repels the electrons. If the collector (anode) is made sufficiently negative the current stops altogether. The voltage at which this first occurs is called the “cutoff voltage”, Vc.

Why does increasing the intensity of light increase the number of photoelectrons emitted but not the energy of each electron?

Increasing the intensity of the light causes more electrons to be knocked out but it doesn’t increase the energy of the individual electrons. Therefore increasing the intensity of the light also does not change the cut-off voltage