When Certain Light Rays Pass from a Vacuum into a Block

Multiple Choice

When certain light rays pass from a vacuum into a block of an unknown material,the measured index of refraction of the material is 3.00.What is the speed of light inside the block?

A) 9.9 × 10⁶ m/s
B) 4.8 × 10⁷ m/s
C) 1.0 × 10⁸ m/s
D) 1.9 × 10⁸ m/s
E) 2.9 × 10⁸ m/s