Visible Light

White light is composed of seven^* bands of wavelengths which can be seen by the human eye as:

red

orange

yellow

green

blue

indigo

violet

Visible light occupies the band of 400 nm to 700 nm of the electromagnetic spectrum. Red has the longest wavelength, violet the shortest.

These colours can be seen when white light passes through a prism.

Graphic by Laura Cohan,
© 1997 Telemetrix
Used by permission

NB: this drawing is not correct and will be part of a quizzz ...

One way to remember the order of the colours of the rainbow is to memorise the menmonic:

ROY G BIV where R stands for red, O stands for orange, ...

Another one is:

Read Only Your Green Book In Verse

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* There is a controversy whether light is made of six or seven bands of wavelengths.
The partisans of six omit the indigo band.

However, visible light still occupies the band of 400 nm to 700 nm!