Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

Why is the Luminous Efficiency Small for a Filament Bulb as Compared to a Mercury Vapour Lamp? - Physics

Advertisement Remove all ads
Advertisement Remove all ads
Advertisement Remove all ads
Short Note

Why is the luminous efficiency small for a filament bulb as compared to a mercury vapour lamp?

Advertisement Remove all ads


In a filament bulb, heat energy is converted into light energy. Most of the electrical energy supplied to the bulb is radiated as heat and only a small percentage is radiated as visible light. Since heat waves are not visible, they don't contribute to visibility. Thus, its luminous flux is lesser than the total radiant flux; hence, its luminous efficiency is low.

In a mercury vapour lamp, a greater amount of electrical energy supplied is converted into visible radiation. Thus, its luminous flux is relatively higher than incandescent lamps.

Concept: Light Process and Photometry
  Is there an error in this question or solution?


HC Verma Class 11, Class 12 Concepts of Physics Vol. 1
Chapter 22 Photometry
Short Answers | Q 6 | Page 453

View all notifications

      Forgot password?
View in app×