The change in direction of a wave as it passes from one medium into another where it travels at a different speed. Refraction is the principle behind lenses in eyeglasses, cameras, microscopes, and telescopes.
Definition
The change in direction of a wave as it passes from one medium into another where it travels at a different speed.
💡 Intuition
A straw looks bent in a glass of water because light bends at the surface.
🎯 Core Idea
Waves bend at boundaries because they travel at different speeds in different media.
Example
Formula
Notation
n_1 and n_2 are the refractive indices (dimensionless), \theta_1 is the angle of incidence, \theta_2 is the angle of refraction, c is the speed of light in vacuum, and v is the speed of light in the medium.
🌟 Why It Matters
Refraction is the principle behind lenses in eyeglasses, cameras, microscopes, and telescopes. It explains why swimming pools appear shallower than they are, why prisms split white light into a rainbow, and how fibre-optic cables guide light over long distances.
💭 Hint When Stuck
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.
Formal View
Related Concepts
🚧 Common Stuck Point
Light bends toward the normal when entering a slower medium.
⚠️ Common Mistakes
- Confusing the direction of bending — light bends toward the normal when entering a denser medium (higher n), not away from it.
- Forgetting that the wave speed changes but the frequency stays the same — it is the wavelength that changes when a wave enters a new medium.
- Applying Snell's law with angles measured from the surface instead of from the normal — all angles must be measured from the perpendicular.
Go Deeper
Frequently Asked Questions
What is Refraction in Physics?
The change in direction of a wave as it passes from one medium into another where it travels at a different speed.
What is the Refraction formula?
When do you use Refraction?
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.
Prerequisites
Next Steps
How Refraction Connects to Other Ideas
To understand refraction, you should first be comfortable with waves and wave speed. Once you have a solid grasp of refraction, you can move on to lenses and total internal reflection.
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