Answer:
Refractive index is 1.43
Explanation:
We are given;
We are required to determine the refractive index of the material.
The speed of light in air is 3.0 × 10^8 m/s
Therefore;
Refractive index = 3.0 × 10^8 m/s ÷ 2.1 × 10^8 m/s
= 1.4286
= 1.43
Thus, the refractive index of the material is 1.43