Reflection of light
Beginner
Angle of incidence equals angle of reflection.
θ_i = θ_rThe reflected ray lies in the plane of incidence and θᵢ = θᵣ, measured from the normal. Rough surfaces scatter light (diffuse reflection).
A ray at 30° to the normal reflects at 30°.
Angles are measured from the normal, not the surface.
In more detail
Reflection of light occurs when light bounces off a surface, with the angle of incidence equal to the angle of reflection. Smooth surfaces reflect specularly, while rough ones scatter diffusely.
Real-world uses
- Mirrors reflect light to form images.
- Road signs use retroreflectors to send light back to the source.
- A periscope uses two mirrors at 45 degrees to bend light, following the reflection rule at each surface.
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Frequently asked questions
Are angles measured from the surface?
No, they are measured from the normal, the line perpendicular to the surface.
Why do rough surfaces look matte?
They scatter light in many directions, so no clear image forms.
Are the angles measured from the surface or the normal?
They are measured from the normal, the line perpendicular to the surface, not from the surface itself.
Related topics in Optics
Nature of light · Rectilinear propagation · Plane mirrors · Spherical mirrors · Mirror equation