Refraction Formula
The Formula
n_1 \sin(\theta_1) = n_2 \sin(\theta_2) (Snell's Law)
When to use: A straw looks bent in a glass of water because light bends at the surface.
Quick Example
Lenses focus light by refraction; a pool looks shallower than it is.
What This Formula Means
The bending of a wave as it crosses the boundary between two media with different wave speeds.
A straw looks bent in a glass of water because light bends at the surface.
Worked Examples
Example 1
mediumLight passes from air (n_1 = 1.0) into glass (n_2 = 1.5) at an angle of incidence of 30°. What is the angle of refraction?
Solution
- 1 Apply Snell's law: n_1 \sin\theta_1 = n_2 \sin\theta_2.
- 2 1.0 \times \sin 30° = 1.5 \times \sin\theta_2
- 3 0.5 = 1.5 \sin\theta_2 \implies \sin\theta_2 = \frac{0.5}{1.5} = 0.333
- 4 \theta_2 = \sin^{-1}(0.333) \approx 19.5°
Answer
\theta_2 \approx 19.5°
Refraction occurs when light changes speed as it enters a different medium. Light bends toward the normal when entering a denser medium (higher refractive index).
Example 2
hardWhat is the critical angle for light going from glass (n = 1.5) to air (n = 1.0)?
Why This Formula Matters
How glasses correct vision, how cameras focus, why prisms make rainbows.
Frequently Asked Questions
What is the Refraction formula?
The bending of a wave as it crosses the boundary between two media with different wave speeds.
How do you use the Refraction formula?
A straw looks bent in a glass of water because light bends at the surface.
Why is the Refraction formula important in Physics?
How glasses correct vision, how cameras focus, why prisms make rainbows.
What do students get wrong about Refraction?
Light bends toward the normal when entering a slower medium.
What should I learn before the Refraction formula?
Before studying the Refraction formula, you should understand: waves, wave speed.