A beam of light in air is incident on the surface of a rectangular block of clear plastic (n = 1.40).If the speed of the beam before it enters the plastic is 3.00 × 10⁸ m/s,what is its speed inside the block? A) 2.14 × 10⁸ m/s B) 2.01 × 10⁸ m/s C) 1.94 × 10⁸ m/s D) 3.00 × 10⁸ m/s

Question

Quizplus · Accepted Answer

The speed of light in a material with refractive index n is given by v = c/n, where c is the speed of light in vacuum. Therefore, the speed of the beam inside the plastic block is:
v = c/n = (3.00 × 10^8 m/s) / 1.40 = 2.14 × 10^8 m/s
Thus, the correct answer is A.

A Beam of Light in Air Is Incident on the Surface