So one of our readers asked us this question the other day: Are light photons emitted by fire the same photons emitted by artificial light such as a light bulb or LED?


The photons are all photons, but there is a difference in the number of photons and the distribution of their energies.

Black Body Radiation Curve

A fire and a classic filament lightbulb produce light in a black body spectrum(see above diagram). At lower temperatures, most of the energy (and most of the photons) are produced in the infrared range, and only a small number of the highest energy photons are produced in the visible range. And, since red photons are lower energy than blue, you’re more likely to produce them, giving a fire it’s characteristic reddish glow.

Heat Vision Googles

In fact, everything radiates like this, not just fire. This is what ‘heat vision goggles’ detects. You are sitting around reading kickassfacts, at about 300 Kelvin, so you produce a black body spectrum that’s pretty much entirely in the infrared.

Normal Cluster Spectrum

An LED, on the other hand, uses some tricks to emit all its energy near the desired wavelength, giving you one color.To reproduce white light (a mixture of all the colors) you have to combine LEDs of multiple wavelengths. This is why ‘white light LEDs’ use so much less energy – instead of using a huge amount of energy to only put out a small amount of visible light (like a blackbody source), they use a small amount of energy to put out a small amount of visible light.

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Last Update: July 7, 2016

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