True or False? Less than 10% of the energy an incandescent bulb is given off as light?

Answer 1

The answer is true. A standard light bulb filament operates at a temperature around 2600 C. At that temperature 6.4% of the total energy is given off as light (93.3% is heat and 0.3% is UV) . Higher filament temperatures mean higher efficiencies. Halogen bulbs are designed to operate up to 5700 C (about the temperature of the Sun's surface) giving an efficiency of 33%. (with 48.3% heat and 18.7% UV). It turns out that this is about the maximum efficiency. Raising the temperature higher ends up producing more UV but not more usable light.

For typical bulbs, as temperature goes up so does efficiency, but just raising temperature can drastically shorten bulb life. A low temperature filament is the easiest way for light bulb manufactureres to make cheap and long lasting bulbs. Thus, most bulbs are very inefficient.

Answer 2

When the thin wire of the bulb get hot ( because of electricity )
it will be shine . but the important point is here :
10% of this shining is light & 90% of this shining is heat ( Infra Red)

Answer 3

If you are talking about a standard, traditional light bulb, yes, that is true.

Answer 4

true. the majority is given off as heat.

Answer 5

true...only 5% is converted into light