"Illumination" essentially refers to lighting, but technically, it  signifies the amount of light required in a specific location to perform  a particular task.

Introduction

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Illumination is a versatile concept, and its significance varies  depending on the task at hand. 

          Defining Illumination

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If a point source of light, which emits equal light in all directions,  is placed at the center of a hollow sphere, the light will fall on its  surface uniformly.

Illustration

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According to this law, the illumination of a surface is inversely  proportional to the square of the distance between the source and the  surface.

1. Inverse Square Law

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2. Lambert Cosine Law

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According to this law, the illumination at any point on a surface is  proportional to the cosine of the angle.

Luminous Flux: This refers to the energy radiations emitted from a light source, such as an electric lamp

        Key Terms in          Illumination

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Illumination: The formula for calculating illumination is straightforward: Illumination (Im) = Luminous Flux (Im) / Area (A). 

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– Luminous Efficiency: The Luminous Efficiency of a light source measures its ability to convert supplied power (in watts) into lumens of light. 

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Depreciation factor: When our lamps, tubes, etc. are  now they give light. With time they are covered with dirt, dust, etc. 

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Lumens: It is the unit of luminous flux and may be  defined as the luminous flux, emitted per unit solid angle, from a light  source of 1 candle power (C.P.)

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