I have done the Solid UV with reflection mode with BaSO4 as background. Now I know the hv but how could I know the required value like alpha to plot the Tauc plot and have the band gap energy.
To calculate the band gap energy from % of reflection data, you need to plot with Kubelka-Munk (K-M) function.
The K-M function is expressed in the equation, 𝐹(R) = (1 ‒ 𝑅)2/2𝑅 (R is the % of reflectance) and the factors for indirect and direct band gap (𝐹(𝑅).𝐸 1/2) and (𝐹(𝑅).𝐸, respectively.