How is white light produced in a tube light?
- ABy heating up the copper wire
- BBy heating up the filament
- CBy accelerating the atoms
- DBy oscillating the molecules
Show answer and explanation
Correct answer: (b) By heating up the filament
Explanation
In a tube light, the filaments at the two ends are heated and give off electrons, which start an electric discharge through mercury vapour at low pressure.
The mercury gives off ultraviolet rays, and the phosphor coating inside the tube turns them into visible white light.
The light itself comes from the mercury discharge and the phosphor coating; heating the filaments starts the discharge.