CFLs contain toxic mercury vapour.
Explanation
Compact Fluorescent Lamps (CFLs) operate on the principle of electric discharge through a gas. Unlike incandescent bulbs, which produce light by heating a tungsten filament (thermal radiation), CFLs produce light through the excitation of mercury vapor.
Detailed Analysis:
- Mechanism of CFLs: A CFL tube contains a mixture of argon gas and a small amount of mercury vapor. When an electric current passes through the tube, it excites the mercury vapor, causing it to emit ultraviolet (UV) light. This UV light strikes the phosphor coating on the inside of the tube, which fluoresces to produce visible light.
- Environmental Hazard: Mercury is a toxic heavy metal. Even small amounts of mercury can be hazardous to human health (neurotoxin) and the environment. When CFLs are disposed of in landfills or broken, the mercury vapor can escape or leach into the soil and groundwater.
- Comparison with Incandescent Bulbs: Traditional incandescent bulbs consist primarily of a glass envelope, a tungsten filament, and inert gases like argon or nitrogen. They do not contain toxic heavy metals like mercury, making their disposal less hazardous in terms of chemical toxicity.
Analysis of Incorrect Options:
- CFLs contain lead filaments. Incorrect: CFLs do not use lead filaments. Incandescent bulbs use tungsten filaments.
- CFLs are made of non-biodegradable plastic only. Incorrect: While CFLs contain plastic and glass components which are non-biodegradable, the primary reason they are classified as "hazardous waste" is specifically the presence of mercury, not the plastic content.
- CFLs emit radioactive radiation after fusing. Incorrect: CFLs do not emit radioactive radiation. They emit UV radiation internally, which is converted to visible light by the phosphor coating.
Key Takeaway:
The disposal of CFLs requires special care because they contain toxic mercury vapor, which poses significant environmental and health risks if released, unlike the inert components of traditional incandescent bulbs.