Electromagnetic radiation is incident on a negatively charged metal plate. No photoelectrons are emitted when high-intensity red light from a lamp is used, but electrons are emitted immediately when a low-intensity ultraviolet source is used.
Explain these observations in terms of the photon model of light.
The maximum wavelength of electromagnetic radiation incident on the surface of a metal plate that causes electrons to be emitted (the threshold wavelength) is 3.3×10−7 m3.3 \times 10^{-7}\text{ m}3.3×10−7 m.
Calculate the maximum kinetic energy, in joules, of the electrons emitted from the surface of this metal plate when each incident photon has an energy of 4.8 eV4.8\text{ eV}4.8 eV.
