Tauc's plot can be used to determine the optical bandgap. The relationship between the absorption coefficient and the optical band gap for direct allowed transition can be expressed from the equation:
(αhυ)2 = C(hυ-Eg)
where C is an energy-independent constant. By plotting (αhυ)2 versus hυ, the values of the optical band gap (Eg) can be calculated from the extrapolated linear portion of the plot for the samples.