Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R).
Assertion (A): Kerosene has a higher refractive index (1.44) than water (1.33).
Reason (R): The refractive index of a medium depends on its mass density: the greater the mass density, the greater the speed of light through it.
- ABoth (A) and (R) are true, and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true, but (R) is not the correct explanation of (A)
- C(A) is true, but (R) is false
- D(A) is false, but (R) is true
Show answer and explanation
Correct answer: (c) (A) is true, but (R) is false
Explanation
(A) is true and (R) is false.
- (A): kerosene's refractive index (about 1.44) is higher than water's (about 1.33). So kerosene is optically denser, even though it is lighter and floats on water.
- (R): refractive index depends on optical density, not on mass density. Also, light slows down in an optically denser medium (n = c/v), so a higher refractive index means a lower speed of light, not a higher one.