Reflection Simulator
About
This simulation places you in front of a golden protractor laid flat on a mirror surface. A flashlight sits to the upper left, casting a beam of light toward the reflection point at the centre of the protractor. Drag the flashlight to any position and watch the reflected ray instantly update — always on the opposite side of the normal, at the same angle.
The law of reflection states that the angle of incidence (θᵢ) equals the angle of reflection (θᵣ), where both angles are measured from the normal — a line perpendicular to the mirror surface at the point where the ray strikes. This relationship holds for every position you drag the flashlight to, demonstrating that specular reflection is perfectly predictable and angle-preserving.
Learning Goals
- State the law of reflection (θᵢ = θᵣ) and verify it by dragging the flashlight to multiple positions around the protractor.
- Identify the normal line and explain its role as the reference line from which incidence and reflection angles are measured.
- Measure and compare the angle of incidence with the angle of reflection and confirm they are always equal.
- Describe what happens at 0° (perpendicular incidence — beam reflects straight back) and at grazing angles (beam skims the surface).
How to Use
- Drag the flashlight — click or touch the grey flashlight body and drag it to any position above the mirror. The incident ray, reflected ray, and angle readout all update in real time.
- Read the angles — look at the protractor scale and the angle readout panel to confirm θᵢ = θᵣ at the current flashlight position.
- Try extreme positions — drag the flashlight directly above the reflection point (90° incidence) and then near the mirror surface (grazing angle). Notice how the reflected ray changes.
- Extend the reflected ray — drag the white handle at the tip of the reflected ray to lengthen it, so you can trace where a reflected beam would travel across the scene.