Define the work function of a metal.
The work function of lithium is 2.5 eV2.5\text{ eV}2.5 eV.
Lithium emits electrons from its surface when blue light is incident on it. However, extremely intense red light produces no electrons.
Explain these observations in terms of photons and their energy.
Monochromatic light from a laser is incident on a lithium target in an evacuated chamber. Electrons are emitted from the surface. The wavelength of the incident light is 300 nm300\text{ nm}300 nm.
Calculate the shortest de Broglie wavelength of the emitted electrons.
