diff --git a/physics/photoelectric_effect.py b/physics/photoelectric_effect.py new file mode 100644 index 000000000..3a0138ffe --- /dev/null +++ b/physics/photoelectric_effect.py @@ -0,0 +1,67 @@ +""" +The photoelectric effect is the emission of electrons when electromagnetic radiation , +such as light, hits a material. Electrons emitted in this manner are called +photoelectrons. + +In 1905, Einstein proposed a theory of the photoelectric effect using a concept that +light consists of tiny packets of energy known as photons or light quanta. Each packet +carries energy hv that is proportional to the frequency v of the corresponding +electromagnetic wave. The proportionality constant h has become known as the +Planck constant. In the range of kinetic energies of the electrons that are removed from +their varying atomic bindings by the absorption of a photon of energy hv, the highest +kinetic energy K_max is : + +K_max = hv-W + +Here, W is the minimum energy required to remove an electron from the surface of the +material. It is called the work function of the surface + +Reference: https://en.wikipedia.org/wiki/Photoelectric_effect + +""" + +PLANCK_CONSTANT_JS = 6.6261 * pow(10, -34) # in SI (Js) +PLANCK_CONSTANT_EVS = 4.1357 * pow(10, -15) # in eVs + + +def maximum_kinetic_energy( + frequency: float, work_function: float, in_ev: bool = False +) -> float: + """ + Calculates the maximum kinetic energy of emitted electron from the surface. + if the maximum kinetic energy is zero then no electron will be emitted + or given electromagnetic wave frequency is small. + + frequency (float): Frequency of electromagnetic wave. + work_function (float): Work function of the surface. + in_ev (optional)(bool): Pass True if values are in eV. + + Usage example: + >>> maximum_kinetic_energy(1000000,2) + 0 + >>> maximum_kinetic_energy(1000000,2,True) + 0 + >>> maximum_kinetic_energy(10000000000000000,2,True) + 39.357000000000006 + >>> maximum_kinetic_energy(-9,20) + Traceback (most recent call last): + ... + ValueError: Frequency can't be negative. + + >>> maximum_kinetic_energy(1000,"a") + Traceback (most recent call last): + ... + TypeError: unsupported operand type(s) for -: 'float' and 'str' + + """ + if frequency < 0: + raise ValueError("Frequency can't be negative.") + if in_ev: + return max(PLANCK_CONSTANT_EVS * frequency - work_function, 0) + return max(PLANCK_CONSTANT_JS * frequency - work_function, 0) + + +if __name__ == "__main__": + import doctest + + doctest.testmod()