The arc lamp produces light by which mechanism?

The arc lamp produces light by which mechanism?

• A. Dielectric breakdowns
• B. Incandescence of a filament
• C. Phosphorescence
• D. Chemiluminescence

Answer: (A)

Light in an arc lamp comes from a discharge through ionized gas. When a high voltage is applied across the lamp, the gas between the electrodes undergoes dielectric breakdown, turning into a plasma that conducts electricity. As the electric arc flows, the extremely hot plasma and the excited gas atoms emit photons, producing the bright light. This is different from heating a filament (incandescence), which relies on the filament’s temperature; from phosphorescence, which is light released after a material is excited and then slowly dimmed; or from chemiluminescence, which is light produced by a chemical reaction. The essential idea is that the light arises from a gas discharge in the lamp, initiated by dielectric breakdown.

Light in an arc lamp comes from a discharge through ionized gas. When a high voltage is applied across the lamp, the gas between the electrodes undergoes dielectric breakdown, turning into a plasma that conducts electricity. As the electric arc flows, the extremely hot plasma and the excited gas atoms emit photons, producing the bright light. This is different from heating a filament (incandescence), which relies on the filament’s temperature; from phosphorescence, which is light released after a material is excited and then slowly dimmed; or from chemiluminescence, which is light produced by a chemical reaction. The essential idea is that the light arises from a gas discharge in the lamp, initiated by dielectric breakdown.