3aafea85_lighting___Energy_Saving_Trust__Lighting_technology
[Description] Traditional light bulbs, also known as tungsten filament, incandescent or GLS (General Lighting Service) bulbs were invented more than 100 years ago and are extremely inefficient. Only about 5 per cent of the electricity they use is converted into visible light. The filament is heated up until it glows giving off a yellowish white light. The bulbs do not last long because the filament gradually evaporates. [Lighting technology] 
Traditional light bulbs
Energy efficient lighting | Energy Saving Trust
Lighting technology