Refraction Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Refraction.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The change in direction of a wave as it passes from one medium into another where it travels at a different speed.

A straw looks bent in a glass of water because light bends at the surface.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Waves bend at boundaries because they travel at different speeds in different media.

Common stuck point: Light bends toward the normal when entering a slower medium.

Sense of Study hint: When solving a refraction problem, first identify the two media and their refractive indices n_1 and n_2. Then apply Snell's law: n_1 \sin\theta_1 = n_2 \sin\theta_2. Remember that light bends toward the normal when entering a denser (slower) medium and away from the normal when entering a less dense (faster) medium.

Worked Examples

Example 1

medium
Light 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. 1
    Apply Snell's law: n_1 \sin\theta_1 = n_2 \sin\theta_2.
  2. 2
    1.0 \times \sin 30° = 1.5 \times \sin\theta_2
  3. 3
    0.5 = 1.5 \sin\theta_2 \implies \sin\theta_2 = \frac{0.5}{1.5} = 0.333
  4. 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

hard
What is the critical angle for light going from glass (n = 1.5) to air (n = 1.0)?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Light travels from water (n = 1.33) into air (n = 1.0) at an angle of incidence of 30°. What is the angle of refraction?

Example 2

hard
Light enters a diamond (n = 2.42) from air (n = 1.00) at an angle of incidence of 45°. Find the angle of refraction. Then calculate the critical angle for light leaving diamond into air.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

waveswave speed