Colour

Red and orange and yellow and green - as heard in the nursery song 'I can sing a rainbow' we live in a world vibrant with colour. This ranges from red (700nm) to violet (400nm) in our visible spectrum; a specific region within the electromagnetic spectrum of light. We see the colours of objects as they reflect certain wavelengths from this spectrum, and photoreceptors (rods and cones) in our eyes are waiting to detect them. Humans have three types of cones, but some species such as birds and fish, have four, allowing them to detect and respond to signals invisible to us, such as ultraviolet light.

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