Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Refractive index of glass is higher than that of air. Reason (R): Optical density of a medium is directly proportionate to its mass density which results in a proportionate refractive index. In the light of the above statements, choose the most appropriate answer from the options given below:

(A) is correct but (R) is not correct

Both (A) and (R) are correct and (R) is the correct explanation of (A)

(A) is not correct but (R) is correct

Both (A) and (R) are correct but (R) is not the correct explanation of (A)

Geometrical Optics PYQ — JEE Main 2025 · 7 Apr · Shift 2 · Q54 with Solution

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Correct answer: B

Evaluate Assertion (A):
Assertion: Refractive index of glass is higher than that of air.

This is true. Typically, $n_{\text{air}} \approx 1.0003, \qquad n_{\text{glass}} \approx 1.5$ Hence, $n_{\text{glass}} > n_{\text{air}}$ So, Assertion (A) is correct.
Evaluate Reason (R):
Reason: Optical density of a medium is directly proportionate to its mass density which results in a proportionate refractive index.

This statement is not generally correct.
- Optical density refers to how much a medium slows down light, and it is related to the refractive index.
- It is not necessarily directly proportional to mass density.
- There are substances with higher mass density but lower refractive index than others, so no universal direct proportionality exists.
Thus, Reason (R) is incorrect.
Choose the correct option:

Since:
- (A) is correct
- (R) is not correct
the correct option is: $\boxed{\text{B}}$
Compare with stored correct answer:
Stored correct answer = B
Derived answer = B

Therefore, they agree.