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The refractive index of ethanol is 1.36. Using v equals c over n, what is the speed of light in ethanol?

A2.21 x 10^8 m/s
B4.08 x 10^8 m/s
C1.36 x 10^8 m/s
D3.00 x 10^8 m/s
Answer & Solution
Correct answer: A. 2.21 x 10^8 m/s
1. The speed of light in a material is v = c/n. 2. Substituting values: v = (3.00 x 10^8 m/s) / 1.36. 3. Carrying out the division gives v = 2.21 x 10^8 m/s. 4. 4.08 x 10^8 m/s would require multiplying by 1.36 instead of dividing, giving a speed faster than light in a vacuum, which is impossible. _Source: OpenStax Physics (CC BY 4.0), Ch 16 "Mirrors and Lenses", section 16.2 Refraction_
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