Dispersive Power — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Dispersive Power Applicable to the material of a prism to measure its ability to disperse white light into its constituent colors. Start with the definition: Ratio of angular dispersion to mean deviation. Angular dispersion (delta v - delta r) = (n v - 1)A - (n r - 1)A = (n v - n r)A. Mean deviation (delta y) = (n y - 1)A. Divide angular dispersion by mean deviation to cancel out the prism angle A. Depends only on the material of the prism, not on the refracting angle of the prism. Assumes n v > n r. n y is typically the arithmetic mean of n v and n r if not explicitly given. Thinking dispersive power depends on the angle of the prism. Confusing dispersive power with angular dispersion (which does depend on the prism angle).