What are Photo Electrons?

When light strikes a clean material’s surface, electrons are emitted from that surface under some specific conditions. This phenomenon is well known as the photoelectric effect. The electrons are called photo-electrons. When light strikes on the surface electrons of the material gain sufficient energy from light to overcome the work function of the material and hence emitted from the surface.

What is work function?

It is defined as the minimum energy required to remove an electron from its shell (outer most shell of the atom). It is measured in eV (Electron-volt). According to classical physics the number of emitted electrons and their momentum is independent of the frequency at which the light strikes the material, but it depends upon the intensity of the incident light energy.

But in actual experiment this statement of classical physics could not be observed. Instead, it is observed that for a particular incident light intensity, the kinetic energy of the emitted electrons varies with the variation of the frequency of the incident light. That means if the frequency of incident light is changed without changing its intensity, then the kinetic energy of emitted electrons or photo-electrons also changes.

What are photo-electrons?

When light energy of sufficient intensity strikes on a surface of material, some electrons of the material very close to the surface, gain sufficient energy to overcome the work function of the material and are emitted from the surface with kinetic energy. These emitted electrons are called photo-electrons. It is also observed that, above a certain frequency of the incident light, the electrons better to say photo-electrons start emitting. This is the minimum frequency of incident light below which no photo-electrons is produced. But above this minimum frequency, the kinetic energy of the electrons varies linearly with frequency. It is also observed that when intensity of incident light is changed by keeping its frequency constant, the rate of photo-electrons emission changes accordingly but the maximum kinetic energy of electrons remains unchanged. In 1900, German Physicists Max Karl Ernst Ludwig Planck stated that the heat radiation from a hot body surface is in the form of discrete packet of energy and these packets of energy are called quanta. This quantity of energy consisting in a single quanta or emitted packet of energy is hf where f is the frequency of radiation and h is the constant called Planck constant that is the quantity of energy, donor impurity in semiconductor Quantum energy is proportional to the frequency of radiation. The value of Planck constant is In 1905 another famous German physicist Sir Albert Einstein stated that the light also consists of energy packet and this packets were referred as photons. The energy content in the photon is also given by same equation and that is
E = hf or E proportional to f.
Only difference is that here the frequency is the frequency of light.

As per this theory, when a light strikes on a material surface, photons with sufficient energy (when frequency is sufficient as E proportional to frequency) knock electrons on the surface of the material. The electrons gain sufficient energy to be removed from the surface, after overcoming the work function of the material. The rest of the energy in a photon is consumed to gain the kinetic energy of the electron. The maximum kinetic energy of an electron can be represented as Where, hf0 is the work function or minimum energy required to remove the electron. h0 is the minimum frequency of incident light below which no electron is removed from the surface.
The photons energy or energy consisting in a photon of a particular light is proportional to the frequency of that light and hence that is inversely proportional to the wavelength of the light wave

Closely Related Articles Amplifier Gain | Decibel or dB GainIntegrated Circuits | Types of ICRegulated Power SupplyLaser | Types and Components of LaserWork FunctionMobility of Charge CarrierElectron volt or eVEnergy Quanta | Development of Quantum Physics Schottky EffectHeisenberg Uncertainty PrincipleSchrodinger Wave Equation and Wave FunctionCyclotron Basic Construction and Working PrincipleSinusoidal Wave SignalCommon Emitter AmplifierRC Coupled AmplifierDifferential AmplifierWave Particle Duality PrincipleSpace ChargeMore Related Articles Vacuum Diode History Working Principle and Types of Vacuum DiodePN Junction Diode and its CharacteristicsDiode | Working and Types of DiodeDiode CharacteristicsHalf Wave Diode RectifierFull Wave Diode RectifierDiode Bridge RectifierWhat is Zener Diode?Application of Zener DiodeLED or Light Emitting DiodePIN Photodiode | Avalanche PhotodiodeTunnel Diode and its ApplicationsGUNN DiodeVaractor DiodeLaser DiodeSchottky DiodePower DiodesDiode ResistanceDiode Current EquationIdeal DiodeReverse Recovery Time of DiodeDiode TestingMOSFET | Working Principle of p-channel n-channel MOSFETMOSFET CircuitsMOS Capacitor | MOS Capacitance C V CurveApplications of MOSFETMOSFET as a SwitchMOSFET CharacteristicsPower MOSFETHalf Wave RectifiersFull Wave RectifiersBridge RectifiersClamping CircuitTheory of SemiconductorIntrinsic SemiconductorExtrinsic SemiconductorsEnergy Bands of SiliconDonor and Acceptor Impurities in Semiconductor Conductivity of SemiconductorCurrent Density in Metal and Semiconductor Intrinsic Silicon and Extrinsic SiliconP Type SemiconductorN Type SemiconductorP N Junction Theory Behind P N JunctionForward and Reverse Bias of P N JunctionZener BreakdownAvalanche BreakdownHall Effect Applications of Hall EffectGallium Arsenide SemiconductorSilicon SemiconductorTypes of TransistorsBipolar Junction Transistor or BJTBiasing of Bipolar Junction Transistor or BJTTransistor BiasingTransistor CharacteristicsCurrent Components in a TransistorTransistor Manufacturing TechniquesApplications of Bipolar Junction Transistor or BJT | History of BJTTransistor as a SwitchTransistor as an AmplifierJFET or Junction Field Effect Transistorn-channel JFET and p-channel JFETApplications of Field Effect TransistorDIAC Construction Operation and Applications of DIACTRIAC Construction Operation and Applications of TRIACPhototransistorNew Articles Series and Parallel Inductors Electric PowerMeasurement of Losses in Shunt ReactorThree Phase Shunt ReactorMeasurement of Insulation ResistanceAmpere's Circuital Law
electrical engineering app