To investigate the Lambert’s distance law.



This law states that the iradiance(luminance) of the radition emitted by a point source decreases with the square of the distance.

Where ,   E = irradiance at the measuring point

L= Distance of the measuring point from the point source in m.


  1. Heat Source.
  2. Thermopile for measuring the radiatio,on rotating mounting.
  3. Luxmeter for measuring the luminous intensity on rotating mounting.
  4. Absorption plates with temperature measurement points.
  5. Colour filters(red,yellow,infrared) and an aperture with clamping mount.
  6. Swevelling light source.
  7. Frame for the components.