Refraction through Prism — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Refraction through Prism.

Combined problems of prism and critical angle/TIR

high

NEET often tests the integration of concepts. A question might involve a prism where light is incident at a certain angle, and then ask for the condition (e.g., maximum angle of incidence) for the light to undergo total internal reflection at the second surface, or to just emerge. This requires calculating the critical angle and comparing it with $r_2$. This tests a deeper understanding of light's behavior at interfaces.

Graphical analysis of deviation vs. incidence angle

medium

While the U-shaped graph is a standard concept, questions might ask for specific interpretations, such as identifying the minimum deviation point, or explaining why there are two angles of incidence for a given deviation (other than minimum deviation). This tests conceptual clarity beyond just formula application.

Dispersion and angular dispersion calculations

medium

Beyond just knowing that dispersion occurs, NEET could ask for calculations related to angular dispersion, which is the difference in deviation for two extreme colors (e.g., violet and red). This involves using the thin prism formula for different refractive indices for different colors, $\delta_V = (\mu_V - 1)A$ and $\delta_R = (\mu_R - 1)A$, and then finding $\delta_V - \delta_R$.

Prism in a liquid medium

low

Instead of air, the prism might be immersed in a liquid with a different refractive index. This changes the relative refractive index $\mu_{prism}/\mu_{liquid}$ in Snell's law, making calculations slightly more complex. This tests the fundamental understanding of relative refractive index and its application in Snell's law.