Compact Fluorescent Lamps (CFL) and Incandescent Lamps are used for lighting applications. Their shapes vary due to the different methods used for producing light. They produce light by two different processes known as fluorescence and Joule heating respectively.
Compact fluorescent lamps produce light by a method called fluorescence. The lamps contain mixture of argon and mercury vapors held at low pressure. The mixture contained in the bulb when excited produces ultraviolet waves. These UV waves stimulate the fluorescent coating inside the bulb. This coating that looks like a white coating absorbs the ultraviolet energy and produces visible light. Fluorescent lamps come in different shapes like conventional and lengthy type and compact CFLs. It is one of the most efficient energy savers.
Incandescent bulb functions on another process. Emission of light by a body because of its high temperature is known as incandescence. This is a kind of thermal radiation. These types of bulbs contain a light thin metal filament connected on both sides by two wires, anode and cathode, which are in turn connected to metal contacts. The filament is made of tungsten which is an electrical resistor. The filament gets hot because of resistor characteristics when electricity is passed through it and the process is called Joule heating. In Incandescence, a fraction of light falls in visible spectrum while majority is in infrared part. The efficiency can be increased by increasing the temperature of the filament, but currently no material is available to withstand such high temperature.
The heat generated in in an incandescent lamp because of hot tungsten filament needs to be dissipated effectively and evenly in all directions. The simple geometry of a spherical glass shell is best suited for this purpose. In a CFL, UV radiation is produced along the length of the lamp, irrespective of the shape. The florescent coating along the length of lamp converts UV waves to light. Unlike in the incandescence bulbs, no heat energy is produced in CFLs. Thus, CFL offers lot of freedom in designing the shape of the lamp.
Even then, shapes play vital roles in power ratings, light output etc. The conventional fluorescent lamps were very lengthy. Philips Lighting is pioneers in the field of luminescent lighting. They are global leaders in all areas related to lighting and has brought in many innovations in the field through their various products and services. Around 1970s, their researchers developed various methods and models to achieve miniaturization in lamp dimensions and geometry. This resulted in the present day shapes and designs of CFLs. These shapes are developed by light engineers considering factors such as efficiency, cost effectiveness, light output, power ratings etc. What is the structure of incandescent light bulbs?