Wave Optics — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Wave Optics.

Combined effects in YDSE

high

NEET often tests the combined effect of multiple changes in YDSE. For example, what happens to fringe width if both wavelength and slit separation are changed, or if the apparatus is immersed in a medium and then a thin film is introduced. These questions require a thorough understanding of the formula $\beta = \frac{\lambda D}{d}$ and how each parameter affects it, especially the change in wavelength in a medium or due to a thin film. Students need to be adept at multi-step calculations and conceptual reasoning.

Intensity distribution and coherence

medium

Questions on intensity in interference patterns, particularly when sources have different intensities ($I_1 \ne I_2$), are a good test of conceptual understanding beyond simple formula application. The relationship $I \propto A^2$ and the addition of amplitudes ($A_{max} = A_1 + A_2$, $A_{min} = |A_1 - A_2|$) are key. Also, questions distinguishing between coherent and incoherent sources, and their respective intensity patterns, are likely to appear, probing fundamental understanding of superposition.

Resolving power of optical instruments

low

While less frequent than YDSE or polarization, questions on the resolving power of telescopes or microscopes, which are limited by diffraction, can appear. These questions typically involve Rayleigh's criterion and the formulas for angular resolution ($\theta = 1.22\lambda/D$ for telescope, $d_{min} = \frac{\lambda}{2n\sin\beta}$ for microscope). Students should be familiar with these formulas and the factors affecting resolving power, such as wavelength and aperture size. It's a good differentiator for top ranks.