Added Photoelectric effect equation

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(name="maximum_kinetic_energy")