Question

What must electrons near the metal surface overcome before they can escape?

Options

• The ultraviolet light from an arc lamp

• The attraction of the positive ions in the material of the surface

• The production of electromagnetic waves by a spark discharge

• The high-voltage sparks across the detector loop

Answer 1

Electrons must absorb enough energy from incident radiation to overcome the attraction of the positive ions in the material. Once they have sufficient energy, they can escape from the metal surface.