[harshita]

Good illumination or lighting is necessary for all buildings and has three primary aims.

• To promote work and other activities carried out within the building;
  
• To promote the safety of the people using the building
  
• To create, in conjunction with the structure and decoration, a pleasing environment conducive to interest of the occupants and a sense of their well-being.
  

Illumination can transform the night-time appearance of a building or landscape. The aesthetics, usability and desirability of a structure or place can be increased by good illumination design.


Electromagnetic radiation spectrum

Visible spectrum

To know more about illumination read .... http://frontdesk.co.in/building-science/illumination-in-architecture/