Photoelectric Effect

Also called

photoelectrons · photon · threshold frequency · stopping potential · work function · Einstein's photoelectric equation · Hertz and Lenard · emitter plate · collector · photocell · intensity and frequency · kinetic energy of photoelectrons · quantum of light · dual nature of radiation · प्रकाश विद्युत प्रभाव · फोटॉन · देहली आवृत्ति

Topics

• Light falling on a metal can knock electrons out of it: the photoelectric effect.
• Below a threshold frequency ν₀ no electrons come out, however bright the light or however long it shines.
• Above the threshold, emission is instant (within a nanosecond), even for very faint light.
• Brighter light of the same frequency frees more electrons per second, but not faster ones.
• The maximum kinetic energy of the electrons rises with the frequency of the light, not with its intensity.
• A reverse voltage slows the electrons; at the stopping potential V₀ even the fastest stop: K_max = eV₀.
• Einstein: light arrives as photons of energy hν; one photon gives all its energy to one electron.
• Einstein's equation hν = φ₀ + K_max: the work function φ₀ = hν₀ is the least energy needed to escape.
• A graph of K_max (or V₀) against frequency is a straight line of slope h starting at ν₀.

About this model

A GLB file of about 287 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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