Solved UPSC CDS/OTA Question
A solved UPSC CDS/OTA PYQ - decoded step-by-step.
Solve it the standard way once - then learn the shortcut.
Q · Units and DimensionsMedium · 45s
Which of the following quantities is dimensionless?
TopicUnits and Dimensions
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained - no skipped algebra.
Refractive index = Speed of light in vacuum / Speed in medium
It is a ratio of two same quantities, so it has no dimension → dimensionless.
Final Answer: Option A - Refractive index