Lectures delivered at Nine Education, Neredmet to of Batch 2026.
Clarification: Meaning of achromatic combination was not answered correctly in class.
An achromatic combination of prisms refers to an arrangement of two prisms made of different materials (typically with different dispersive powers) such that the net dispersion is zero while a finite deviation still occurs. In simple terms, when white light passes through the combination, it is bent (deviated) as a whole but not split into its constituent colors, so no spectrum is formed. This is achieved by choosing the prism angles and materials so that the angular dispersion produced by one prism is exactly cancelled by the other, even though their individual deviations add up. Mathematically, the condition for achromatism is A_1 * w_1 = A_2 * w_2 where w is dispersive power and A is the prism angle.
Topics covered :
- Discussion on dispersion due to prism
- Some important points
- Problems on dispersion
