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

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Quizplus · Accepted Answer

The speed of light in a medium is given by v = c/n, where c is the speed of light in a vacuum (3.00 x 10^8 m/s) and n is the refractive index of the medium. For plastic with n = 1.40, the speed is 3.00 x 10^8 m/s / 1.40 = 2.14 x 10^8 m/s.

A Beam of Light in Air Is Incident on the Surface