Photometry

• Photometry is a branch of physics which deals with the measurement of light energy. It has assumed importance in our daily life as every place (e.g. study room, bed room, laboratory, theatre, park etc.) requires a definite illumination in order to avoid unnecessary strain on our eyes. In this connection following terms are to be clearly understood:
• (a) Luminous Intensity of a source and Luminous flux
• (b) Efficiency of a source
• (c) Illuminance or Intensity of Illumination 
• (d) Luminance or Brightness