MCQ Detailed View

The correct answer is Illumination. Lambert’s law, also known as the Lambert cosine law, is a fundamental principle in optics that describes how the intensity of light on a surface varies with the angle at which it strikes the surface. According to the law, the apparent brightness or illumination of a perfectly diffusing (matte) surface is directly proportional to the cosine of the angle between the incident light and the normal to the surface.

Mathematically, Lambert’s law is expressed as:

I=I0cos⁡θI = I_0 \cos \thetaI=I0cosθ

Where:

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  $I$ = illumination on the surface

  
  


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  I0I_0I0 = illumination if light falls perpendicular to the surface

  
  


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  $\theta$ = angle between the light direction and the normal to the surface

  
  

This law is crucial in fields like photometry, computer graphics, photography, and lighting design because it predicts how surfaces appear under different lighting conditions. For example, a surface appears brightest when the light hits it directly (perpendicular) and dimmer at shallow angles.

Lambert’s law is not related to reflection, refraction, or interference directly. While reflection and refraction deal with the change in light direction when interacting with surfaces or media, Lambert’s law specifically quantifies how light spreads over a surface and how the intensity decreases with the angle. Interference is a phenomenon of wave superposition, which is unrelated to Lambert’s law.

In practice, Lambert’s law helps in designing illumination systems, calculating solar energy incident on panels, and in rendering realistic images in computer graphics, ensuring that light behaves naturally on matte surfaces.

🔑 Key Facts:

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  Lambert’s law = cosine law of illumination.

  
  


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  Illumination decreases as light hits the surface at an angle.

  
  


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  Brightest illumination occurs when light is perpendicular.

  
  


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  Important in photometry, computer graphics, and lighting.

  
  


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  Not related to reflection, refraction, or interference.

  
  

👉 Final Answer: Lambert’s law is related to Illumination.