Brainlag PlusThe law of reflection, why a change of speed bends a wave towards or away from the normal, and wavefronts.
Reflection
When a wave hits a smooth surface it bounces off at the same angle it arrived at.
The normal is an imaginary line at 90° to the surface where the ray hits it. Every angle in a ray diagram is measured from the normal.
angle of incidence = angle of reflection
- A ray makes 25° with a mirror's surface
- angle of incidence = 90° − 25° = 65°
- angle of reflection = 65°
- angle between the two rays = 65° + 65° = 130°
At any boundary a wave can also be transmitted (it passes through) or absorbed (the material takes its energy). Most real boundaries do a mix of all three.
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 5, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- The Refraction simulation beside every question
- Anything you get wrong is saved to your flashcards