law of reflection

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Diagram showing light from a bee reflecting off a vertical plane mirror into an observer's eye; equal angles of incidence and reflection produce a virtual bee image behind the mirror.

law of reflection

optics

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July 13, 2026

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Diagram showing light from a bee reflecting off a vertical plane mirror into an observer's eye; equal angles of incidence and reflection produce a virtual bee image behind the mirror. — reflection of light in a mirror According to the law of reflection, images are reflected from a smooth surface, such as a mirror, at the same angle (θ₂) as the incidence angle (θ₁). When the eye “sees” an object in three-dimensional space in a mirror, it is actually viewing an image along sight lines created by the reflection of light from the surface of the mirror.

The law of reflection is a fundamental principle in optics that describes how light behaves when it bounces off a surface. It states that the angle at which light strikes a surface (the angle of incidence) is equal to the angle at which it reflects off the surface (the angle of reflection). Both the incident ray and the reflected ray, along with a line perpendicular to the surface called the normal, all lie within the same plane. This law is crucial for understanding how mirrors work, enabling them to form images by directing light in a predictable way. While smooth surfaces like mirrors follow this law precisely, rough surfaces scatter light diffusely, allowing us to see them from various angles.1234

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angle of incidence
The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray. The angle of incidence equals the angle of reflection. The reflected ray is always in the plane defined by…
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The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray. The angle of incidence equals the angle of reflection. The reflected ray is always in the plane defined by…
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Calculus of Variations
…of Alexandria noticed that the law of reflection—angle of incidence equals angle of reflection—could be restated by saying that reflected light takes the shortest path—or the shortest time, assuming it has finite speed. About 1660 Pierre de Fermat generalized this idea to a least-time principle for all light rays (reintroducing…
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…of Alexandria noticed that the law of reflection—angle of incidence equals angle of reflection—could be restated by saying that reflected light takes the shortest path—or the shortest time, assuming it has finite speed. About 1660 Pierre de Fermat generalized this idea to a least-time principle for all light rays (reintroducing…
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principles of physical science
Manifestations of the extremal principle
The laws of reflection and refraction may be deduced from this principle if it is assumed as Fermat did, correctly, that in a medium of refractive index μ light travels more slowly than in free space by a factor μ. Strictly, the time taken along a…
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The laws of reflection and refraction may be deduced from this principle if it is assumed as Fermat did, correctly, that in a medium of refractive index μ light travels more slowly than in free space by a factor μ. Strictly, the time taken along a…
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optics
Reflection
…polished surface, the angle of reflection between ray and normal (the line at right angles to the surface) is exactly equal to the angle of incidence. It can be seen that a convex mirror forms a virtual image of a distant object, whereas a concave mirror forms a real image.…
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…polished surface, the angle of reflection between ray and normal (the line at right angles to the surface) is exactly equal to the angle of incidence. It can be seen that a convex mirror forms a virtual image of a distant object, whereas a concave mirror forms a real image.…
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