Lambert's Cosine Law Formula

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Illuminance at angle of incidence is also known as the illumination angle of a surface with a light source, such as the Earth's surface and the Sun. Check FAQs
Eθ=Evcos(θi)
Eθ - Illuminance at Angle of Incidence?Ev - Illumination Intensity?θi - Incident Angle?

Lambert's Cosine Law Example

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With units
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Here is how the Lambert's Cosine Law equation looks like with Values.

Here is how the Lambert's Cosine Law equation looks like with Units.

Here is how the Lambert's Cosine Law equation looks like.

0.8833Edit=1.02Editcos(30Edit)
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Lambert's Cosine Law Solution

Follow our step by step solution on how to calculate Lambert's Cosine Law?

FIRST Step Consider the formula
Eθ=Evcos(θi)
Next Step Substitute values of Variables
Eθ=1.02lxcos(30°)
Next Step Convert Units
Eθ=1.02lxcos(0.5236rad)
Next Step Prepare to Evaluate
Eθ=1.02cos(0.5236)
Next Step Evaluate
Eθ=0.883345911860127
LAST Step Rounding Answer
Eθ=0.8833

Lambert's Cosine Law Formula Elements

Variables
Functions
Illuminance at Angle of Incidence
Illuminance at angle of incidence is also known as the illumination angle of a surface with a light source, such as the Earth's surface and the Sun.
Symbol: Eθ
Measurement: NAUnit: Unitless
Note: Value can be positive or negative.
Illumination Intensity
Illumination intensity refers to the level or strength of light in a given area. It quantifies the amount of light reaching a surface and is typically measured in units such as lux or foot-candles.
Symbol: Ev
Measurement: IlluminanceUnit: lx
Note: Value can be positive or negative.
Incident Angle
The incident angle refers to the angle between the impact direction and the solid surface. For a vertical impact, this angle is 90 degrees.
Symbol: θi
Measurement: AngleUnit: °
Note: Value can be positive or negative.
cos
Cosine of an angle is the ratio of the side adjacent to the angle to the hypotenuse of the triangle.
Syntax: cos(Angle)

Other formulas in Laws of Illumination category

​Go Specific Consumption
S.C.=2PinCP
​Go Utilization Factor of Electrical Energy
UF=LrLe
​Go Luminous Intensity
Iv=Lmω
​Go Beer-Lambert Law
It=Ioexp(-βcx)

How to Evaluate Lambert's Cosine Law?

Lambert's Cosine Law evaluator uses Illuminance at Angle of Incidence = Illumination Intensity*cos(Incident Angle) to evaluate the Illuminance at Angle of Incidence, The Lambert's Cosine Law formula is defined as Lambert’s cosine law states that the radiant intensity from the ideal diffusely reflecting surface and cosine of the angle θ between the direction of incident light and surface normal are directly proportional. Illuminance at Angle of Incidence is denoted by Eθ symbol.

How to evaluate Lambert's Cosine Law using this online evaluator? To use this online evaluator for Lambert's Cosine Law, enter Illumination Intensity (Ev) & Incident Angle i) and hit the calculate button.

FAQs on Lambert's Cosine Law

What is the formula to find Lambert's Cosine Law?
The formula of Lambert's Cosine Law is expressed as Illuminance at Angle of Incidence = Illumination Intensity*cos(Incident Angle). Here is an example- 0.883346 = 1.02*cos(0.5235987755982).
How to calculate Lambert's Cosine Law?
With Illumination Intensity (Ev) & Incident Angle i) we can find Lambert's Cosine Law using the formula - Illuminance at Angle of Incidence = Illumination Intensity*cos(Incident Angle). This formula also uses Cosine function(s).
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