Eli5: Why aren’t car headlights green?

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So, people see best in the wavelength around 500nm which is a green/blue color. Why aren’t car headlights this color to improve visibility? Why can’t you buy headlight bulbs that emit bright green light? A white light with a green filter would just make it more dim, but on headlights you want brightness.

In: Technology

9 Answers

Anonymous 0 Comments

I don’t know exactly where the 500nm comes from, but I assume it means that our eyes are most receptive to light with about 500nm wavelengths. However, it is wrong to assume that all light is only a single wavelength. Most light, in fact, is a combination of several wavelengths.

For example, a halogen light (a common choice for headlights) produces every wavelength of light at varying intensities. 500nm is included, but more light simply means more activation.

If you wanted to have a green light, you would need to find a convenient way to produce green light, probably using an LED. However, a green LED headlight is a bad choice – Mostly, a colorblind person might be less receptive to a purely green light as opposed to a full-spectrum light like a halogen light.

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