A beam of light in air is incident on the surface of a rectangular block of clear plastic (n = 1.49).If the velocity of the beam before it enters the plastic is 3.00 x 10⁸ m/s,what is its velocity inside the block? A)3.00 x 10⁸ m/s B)1.93 x 10⁸ m/s C)2.01 x 10⁸ m/s D)1.35 x 10⁸ m/s

Question

Quizplus · Accepted Answer

The velocity of light in a material is given by v = c/n, where c is the speed of light in vacuum and n is the refractive index of the material. 
In this case, the velocity of the beam in the plastic block is: 
v = (3.00 x 10^8 m/s) / 1.49 = 2.01 x 10^8 m/s
Therefore, the answer is choice C.

A Beam of Light in Air Is Incident on the Surface