Unit & Dimensions - NEET Previous Year Questions with Solutions

he dimensional formula of Planck's constant (h) is [M L² T⁻¹]. This comes from E = hν, where energy has dimensions [M L² T⁻²] and frequency (ν) has dimensions [T⁻¹]. Dividing gives h the dimensions [M L² T⁻¹], which is the same as angular momentum — a fact NTA has tested directly.

It should not be skipped. Although only 1–2 questions appear, those are guaranteed scoring opportunities. The concepts are finite — SI units, dimensional formulas, dimensional analysis, and error propagation — and NEET repeats patterns. Students who master this chapter through PYQ practice can answer these questions in under 30 seconds, leaving more time for harder topics

NEET typically includes 1 to 2 questions from Units and Dimensions each year. Occasionally a third question appears when error-in-measurement is tested separately. Since the chapter is short and predictable, solving all PYQs from 2005–2024 is enough to cover the full range of question types NTA uses.

Dimensionless quantities asked in NEET include strain (change in length / original length), refractive index (ratio of speeds), relative density (ratio of densities), angle in radians (arc length / radius), and Reynolds number. All are pure ratios with no units. When a question asks you to identify a dimensionless quantity from four options, check which one is a ratio of identical dimensions.

Based on PYQs from 2010–2024, dimensional formulas of physical quantities and identification of SI units together account for over 70% of all questions from this chapter. Error in measurement (percentage error and propagation) comes next. Dimensional analysis to check equation correctness and unit conversion round out the rest.