The transmission angle will be greater than the incident angle when the speed of Medium 2 is ______ the speed of Medium 1.

The transmission angle will be greater than the incident angle when the speed of Medium 2 is ______ the speed of Medium 1.

• A. Greater than
• B. Less than
• C. Equal to
• D. Cannot say

Answer: (A)

When a wave crosses a boundary, the transmitted (refraction) angle depends on how fast the wave travels in the two media. Snell’s law in terms of speeds says sin θ2 = (v2/v1) sin θ1. If Medium 2 is faster than Medium 1 (v2 > v1), the ratio v2/v1 is greater than 1, so sin θ2 > sin θ1, which means θ2 is larger than θ1. Therefore the transmission angle will be greater when Medium 2 is faster than Medium 1. If the speeds were equal, the angles would be the same; if Medium 2 were slower, θ2 would be smaller.

When a wave crosses a boundary, the transmitted (refraction) angle depends on how fast the wave travels in the two media. Snell’s law in terms of speeds says sin θ2 = (v2/v1) sin θ1. If Medium 2 is faster than Medium 1 (v2 > v1), the ratio v2/v1 is greater than 1, so sin θ2 > sin θ1, which means θ2 is larger than θ1. Therefore the transmission angle will be greater when Medium 2 is faster than Medium 1. If the speeds were equal, the angles would be the same; if Medium 2 were slower, θ2 would be smaller.