Laws of Reflection and Refraction

The Laws of Reflection and Refraction are important principles in illumination that describe how light behaves when it interacts with a surface or a medium. These laws have significant implications for the design and implementation of lighting systems.

Law of reflection

θ₁   = angle of incidence

θ’₁  = angle of reflection.

I – Incident ray

R’ – Reflected ray

R- Refracted ray

N- Normal to the surface

I , R’ ,R ,N are in one plane

The Law of Reflection states that the angle of incidence of a light ray is equal to the angle of reflection of the same ray when it reflects off a smooth surface. This means that if a light ray strikes a smooth surface at a 45-degree angle, it will reflect off the surface at a 45-degree angle in the opposite direction. This law is essential for designing lighting systems that use reflectors or mirrors to direct and control the direction of light.

The Law of Refraction (also known as Snell’s Law) describes how light bends as it passes through a medium with a different refractive index. It states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, known as the refractive index of the medium. This law is important for designing lighting systems that use lenses or prisms to refract or bend light, such as in optical fibers or camera lenses.

θ₂ = angle of refraction;

μ₁ = refractive index of medium 1

μ₂ = refractive index of medium 2

In illumination, these laws are important to consider when designing lighting systems that use reflectors, lenses, or other optical components. For example, the design of a reflector for a luminaire will depend on the angle of incidence and reflection of light, and the design of a lens or prism will depend on the refractive index of the medium and the angle of incidence and refraction of light.

Understanding the Laws of Reflection and Refraction is crucial for the design of efficient and effective lighting systems that produce the desired illumination levels and distribution patterns.

Visual efficiency & comfort

Illumination in architecture – home page

FD Architect Community Forum Discussion

• Illumination – introduction
• Basic Terminology and Definitions
• Laws of Illumination The Inverse Square Law of Illuminance Illuminance (E) at any poi
• Laws of Reflection and Refraction
• Visual efficiency & comfort
• Day lighting
• Components of Daylight Factor
• Artificial Lighting Design

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