Photoelectric Effect and Wave-Particle Duality

Flashcards covering the photoelectric effect, photon energy, work function, and wave-particle duality.

Minimum Photon Frequency for Electron Liberation

The photon's energy, determined by its frequency, must be greater than the work function (energy needed to break bonds holding the electron) in order for an electron to be emitted.

What happens if a photon has a frequency higher than the threshold frequency?

The electron will be liberated, and the remaining energy becomes the kinetic energy of the electron.

Effect of Increasing Light Intensity when Photoelectric Emission Does NOT Occur

Increasing light intensity has no effect because each photon still carries the same amount of energy, which is not enough to liberate an electron.

Work Function

The energy required by an electron to overcome the metallic bond holding it in the metal.

Electron Volt

The kinetic energy of an electron that has been accelerated from rest through a potential difference of 1V.

How a Fluorescent Tube Works

High voltage applied across mercury vapor accelerates fast-moving free electrons, which collide with the mercury atoms, exciting them. Mercury electrons return to the ground state, releasing a UV photon. The tube's phosphorus coating absorbs the UV photons, and its electrons are excited, they cascade down the energy levels and emit visible light photons.

Evidence for Discrete Energy Levels in Atoms

Line emission and absorption spectra, as the lines appear at discrete points which show where a light photon of specific frequency and wavelength has been absorbed or emitted, this shows electrons can only absorb an exact amount of energy to be excited to the next discrete energy level.

Wave-Particle Duality

All particles have both particle and wave properties. Waves can have particle properties, e.g., light acts as a particle in the photoelectric effect and as a wave when it is diffracted.