Ibn al-Haytham's Book of Optics Shaped the Study of Light
In the early 11th century he argued that vision works by light entering the eye and used experiments to show it.
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Hubble's Mirror Was Ground Incorrectly
A flaw of about two micrometers left early images blurry until astronauts installed corrective optics in 1993.
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Eyeglasses Were Invented in Italy in the Late 1200s
The first wearable lenses appeared around 1286, long before the invention of the microscope or telescope.
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Every Human Eye Has a Blind Spot
Where the optic nerve leaves the retina there are no light-detecting cells, but the brain fills in the gap.
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Rainbows Form When Raindrops Bend and Reflect Sunlight
Light refracts as it enters a drop, reflects off the back and splits into colors as it leaves.