Question

Two objects, Object A and Object B, need to be identified. Object A's index of refraction is determined to be 1.77, and Object B's index of refraction is determined to be 1.333. Knowing this information, which of the following must be true? A. Light can pass through Object A faster than it can pass through Object B.
B. The optical density of Object A is lower than the optical density of Object B.
C. Light can pass through Object B faster than it can pass through Object A.
D. The optical density of Object B is higher than the optical density of Object A.

Answer 1

The correct answer is

C. Light can pass through Object B faster than it can pass through Object A.

In fact, the index of refraction of a material is defined as:

$n=\frac{c}{v}$

where c is the speed of light in vacuum and v is the speed of light in the material. Rearranging the equation, we can write the speed of light in the material as:

$v=\frac{c}{n}$

So we that, the smaller the refractive index n, the greater the speed of light in the material, v. In this problem, object B has lower refractive index than object A, so light travels faster in object B.

Answer 2

In the question "Two objects, Object A and Object B, need to be identified. Object A's index of refraction is determined to be 1.77, and Object B's index of refraction is determined to be 1.333. Knowing this information, which of the following must be true? A. Light can pass through Object A faster than it can pass through Object B." The correct answer is "Light can pass through Object B faster than it can pass through object A." (option C) The refractive index is a ratio of the speed of light in a medium relative to its speed in a vacuum. The refractive index of any other medium is defined relative to the refractive index of a vacuum, which is assigned a value of 1. Thus, a refractive index of 1.33 for water means that light travels 1.33 times faster in a vacuum than in water.