What colour is that wavelength?
Visible light occupies less than one octave of the electromagnetic spectrum — a sliver of a range spanning twenty.
Almost exactly a green
550 nm is longer than 5 of the 10 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| X-rays | 1 nm | 550× | |
| ultraviolet | 300 nm | 1.83× | |
| violet | 400 nm | 1.38× | |
| blue | 470 nm | 1.17× | |
| green | 530 nm | 1.04× | |
| yellow | 580 nm | 0.948× | |
| red | 680 nm | 0.809× | |
| near infrared | 1,000 nm | 0.55× | |
| microwave | 10,000,000 nm | 1/18,182 | |
| FM radio | 3,000,000,000 nm | 1/5,454,545 |
Worth knowing
- Visible light runs from about 380 to 750 nanometres — less than a factor of two, so under one octave out of the twenty the spectrum spans.
- The eye is most sensitive at 555 nm, a yellowish green, which is why high-visibility clothing is that colour.
Frequently asked
What wavelength is each colour?
Roughly: violet 380–450 nm, blue 450–495, green 495–570, yellow 570–590, orange 590–620 and red 620–750.
Why can we only see that narrow band?
Because it is the band that passes through water and the atmosphere and carries enough energy to trigger a chemical change without destroying the molecule. Vision evolved in water.