You could call this point 'the ultraviolet spectrum of design': it's there, but imperceptible.

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For example, iron-gall ink, commonly used on ancient documents, is transparent to infra-red light and most visible in the ultraviolet region of the spectrum.

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When the sun is in this state, it also sends less energy out in the soft X-ray and extreme ultraviolet parts of its spectrum.

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These tools span much of the electromagnetic spectrum from X-rays to ultraviolet to the infrared - and of course microscopy with visible light.

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