Why do objects glow red/white when heated?
In: Physics
It’s called incandescence, and it’s a result of visible light being emitted from the higher-energy state the matter is in at a higher temperature.
Something being hotter means that the atoms making it up vibrate faster. Since atoms are made up of positively and negatively charged particles, and the movement of these particles generates electric and magnetic fields. These fields in turn emit photons – which are essentially just packets of electromagnetic energy. When this energy has a frequency in the visible spectrum – the kind of EM radiation that we can see – you perceive this as a glow.
Things that aren’t very hot have lower energy, and hence glow red – red is the least energetic form of light. Things that are a lot hotter also emit the other, higher-energy forms of light, eventually glowing white when they have enough energy to emit all the frequencies we’re capable of seeing.
Edit: As an added fun fact, this is the same reason infrared cameras work. The radiation being emitted follows the exact same principle, but infrared is even less energetic than red light – infrared literally meaning ‘below red’. This to the point that even things at room temperature are hot enough to emit this kind of light – we can’t see it with our eyes, but specialized cameras can, and hotter things emit more infrared light than colder things.
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