Comment by lgeorget
12 hours ago
How does enclosing the lamp in reflective material help with the energy efficiency? Isn't the infrared radiation emitted anyway? Doesn't that make the lamp overheat?
12 hours ago
How does enclosing the lamp in reflective material help with the energy efficiency? Isn't the infrared radiation emitted anyway? Doesn't that make the lamp overheat?
If the reflective material is ideal, by definition no infrared or other radiation is emitted.
Perhaps I was not clear, but the reflective surface was the interior surface, so it reflected any light, visible or infrared, back towards the emitting filament, while the front window reflected only the infrared, while transmitting the visible light.
The lamp does not overheat, because the filament is kept at a constant temperature, the same as in a classic incandescent lamp. The difference is that you need a much lower electrical current through it for maintaining the temperature, because most of the heat is not lost away, like in a classic lamp. The fact that you need a much smaller electrical current for the same temperature is the source of the greater energy efficiency.
Only if you had used the same electrical current as in a classic lamp, the lamp would have overheated and the filament destroyed, but you have no reason to do that, like you also do not want to use in a classic lamp a current higher than nominal, which would overheat and destroy it.