What is the refractive index of a medium?

Last Updated: 25 Jun 2026

What is the refractive index of a medium? Here, the relevant answer is “Speed of light in vacuum/Speed of light in medium.” A sound solution relies on the governing concept rather than a memorised option letter, because option order may change in another paper. The distractors in this question—Speed of light in medium/Speed of light in vacuum, Wavelength in medium/Wavelength in vacuum, Frequency in vacuum/Frequency in medium—do not satisfy the exact condition stated. Students should therefore read every qualifier, including words such as “always,” “at infinity,” “in vacuum,” “per unit,” and “directly proportional.” Such words often decide the correct option. The final selection must agree with the explanation and marked answer: Speed of light in vacuum/Speed of light in medium.

ASpeed of light in medium/Speed of light in vacuum

BSpeed of light in vacuum/Speed of light in medium

CWavelength in medium/Wavelength in vacuum

DFrequency in vacuum/Frequency in medium

Correct Answer: Speed of light in vacuum/Speed of light in mediumYour Answer: B

Explanation

— the scientifically appropriate response is Speed of light in vacuum/Speed of light in medium. Option-wise review: Speed of light in vacuum/Speed of light in medium is correct under the condition given in the stem. Speed of light in medium/Speed of light in vacuum is incorrect because it describes a different quantity or phenomenon and does not meet the stated condition. Wavelength in medium/Wavelength in vacuum is also incorrect; although it may be a valid physics term, its definition or application is not the one asked here. Frequency in vacuum/Frequency in medium is incorrect because it fails the governing relation or characteristic relevant to this case. Therefore, option B, Speed of light in vacuum/Speed of light in medium, is factually and logically consistent with the question. Refractive index n = c/v where c is speed in vacuum and v is speed in medium.

Important Notes

Read the complete stem before looking at the options. Identify whether the demand is a definition, unit, formula, direction, cause, effect, image characteristic, or device principle. In this record, the confirmed answer is Speed of light in vacuum/Speed of light in medium.
Physics answers are condition-dependent. The same lens, force, circuit, wave, or thermodynamic system can behave differently when distance, medium, temperature, direction, or boundary conditions change. Preserve every qualifier in the question.
Do not interchange closely related terms: mass and weight; distance and displacement; speed and velocity; heat and temperature; reflection and refraction; real and virtual image; current and potential difference; power and energy. Such pairs generate common SSC distractors.
Eliminate Speed of light in medium/Speed of light in vacuum, Wavelength in medium/Wavelength in vacuum, Frequency in vacuum/Frequency in medium here because none fulfils the exact requirement of the stem. The final answer and correct-index field must point to option B.
Exam memory point: connect Speed of light in vacuum/Speed of light in medium directly with the key wording of the question, then verify it once against the relevant definition or formula before marking the answer.Higher n means denser medium

Test your SSC CGL Physics knowledge

Start Topic Test

FAQ

SSC CGL Physics FAQs

Common questions and clear answers for this topic.

How many physics questions usually appear in the SSC CGL exam?

Physics typically makes up a small portion of the General Science questions, usually focused on concepts rather than numerical problems.

Which physics topics are most important for SSC CGL?

Basic mechanics, heat, sound and light, and electricity and magnetism are the areas that come up most consistently across previous papers.

Do I need to solve numerical problems for SSC CGL physics?

Rarely. Most questions are conceptual and test everyday understanding rather than calculation skills.

Is NCERT physics enough for SSC CGL preparation?

NCERT textbooks from classes 9 and 10 build a strong enough conceptual base for most of what SSC CGL asks.

How can I make physics concepts easier to remember for SSC CGL?

Connecting concepts to everyday observations, like why a thermos keeps tea warm, makes them far easier to recall than memorizing definitions.

Same Topic MCQs

View All

Which phenomenon is responsible for the formation of mirages?What is the formula for gravitational force between two masses?What is the effect of increasing temperature on the speed of sound in air?