What is Cosine Law

Horace He

Last Updated: December 26, 2023

What is Cosine Law

The cosine law, also known as Lambert’s cosine law or the cosine emission law, is a fundamental principle in the lighting industry. It states that the radiant intensity from an ideal diffusely reflecting surface is directly proportional to the cosine of the angle between the direction of incident light and the surface normal. This law, named after Johann Heinrich Lambert, is studied in optics and plays a crucial role in understanding how light is distributed and how it affects the illumination of a surface.

The cosine law of illumination is used to calculate the illuminance (or irradiance) on a surface based on the angle of incidence. It provides a mathematical relationship that determines the amount of light falling on a surface by considering the angle at which the light hits the surface. By optimizing the placement and direction of light sources, lighting designers and engineers can achieve the desired illumination levels and uniformity on a surface.

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The cosine law of illumination is an important concept in the lighting industry as it helps in the design and implementation of lighting systems. It allows for the calculation of illuminance based on the angle of incidence, enabling the optimization of lighting conditions for various applications. Understanding the cosine law is crucial for achieving efficient and effective lighting solutions.

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