The Photoelectric Effect
Definition:
The photoelectric effect is a phenomenon in which electrons are emitted from a material's
surface when it is exposed to light or electromagnetic radiation, typically in the form of photons. This
effect is a fundamental concept in quantum physics and has significant implications in
understanding the wave-particle duality of light and the behavior of electrons.
Key Contributors:
Heinrich Hertz (1887): First observed the phenomenon that light can induce the emission of
electrons.
Albert Einstein (1905): Proposed the quantum theory of the photoelectric effect and
explained it using the concept of photons.
Key Principles:
Photon Particle Model:
● Einstein proposed that light consists of discrete packets of energy called photons.
The energy (E) of a photon is directly proportional to its frequency (f) and can be
described by the equation E = hf, where h is Planck's constant.
Emission of Electrons:
● When light, with energy greater than or equal to the work function (Φ) of a material,
strikes the surface of the material, it can cause the emission of electrons from the
material.
● Work function (Φ) is the minimum energy required to remove an electron from the
surface of a material. It depends on the material and is often measured in
electronvolts (eV).
Photoelectric Current:
● Electrons emitted from the material surface constitute a photoelectric current (I),
which can be measured using an ammeter.
● The intensity (brightness) of light is directly proportional to the photoelectric current.
Energy Conservation:
● According to the law of conservation of energy, the energy of incident photons is
used to overcome the work function and provide kinetic energy (K.E.) to emitted
electrons. This is expressed by the equation: E = Φ + K.E.
Threshold Frequency:
● To trigger the photoelectric effect, the incident light must have a minimum frequency
called the threshold frequency (f₀).
● If the frequency of light is below the threshold frequency, no electrons will be emitted,
regardless of its intensity.
Definition:
The photoelectric effect is a phenomenon in which electrons are emitted from a material's
surface when it is exposed to light or electromagnetic radiation, typically in the form of photons. This
effect is a fundamental concept in quantum physics and has significant implications in
understanding the wave-particle duality of light and the behavior of electrons.
Key Contributors:
Heinrich Hertz (1887): First observed the phenomenon that light can induce the emission of
electrons.
Albert Einstein (1905): Proposed the quantum theory of the photoelectric effect and
explained it using the concept of photons.
Key Principles:
Photon Particle Model:
● Einstein proposed that light consists of discrete packets of energy called photons.
The energy (E) of a photon is directly proportional to its frequency (f) and can be
described by the equation E = hf, where h is Planck's constant.
Emission of Electrons:
● When light, with energy greater than or equal to the work function (Φ) of a material,
strikes the surface of the material, it can cause the emission of electrons from the
material.
● Work function (Φ) is the minimum energy required to remove an electron from the
surface of a material. It depends on the material and is often measured in
electronvolts (eV).
Photoelectric Current:
● Electrons emitted from the material surface constitute a photoelectric current (I),
which can be measured using an ammeter.
● The intensity (brightness) of light is directly proportional to the photoelectric current.
Energy Conservation:
● According to the law of conservation of energy, the energy of incident photons is
used to overcome the work function and provide kinetic energy (K.E.) to emitted
electrons. This is expressed by the equation: E = Φ + K.E.
Threshold Frequency:
● To trigger the photoelectric effect, the incident light must have a minimum frequency
called the threshold frequency (f₀).
● If the frequency of light is below the threshold frequency, no electrons will be emitted,
regardless of its intensity.
