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Ancient ideas about light

Ancient ideas about light

Pythagoras, Euclid and Ptolemy thought that light moved in straight lines. They also believed the eye emitted visual rays, like feelers, that touched the object and created the sensation of sight.

  • If you drop a needle, it takes a while before you spot it. In the 3rd Century BC, Euclid thought that this delay in vision is caused by the visual ray that is yet to touch the object.
  • The idea was rejected by Ptolemy the Second in the 10th Century. He thought something emitted by an object (like the sun) must have entered the eye.


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Two theories of light: particle and wave

Huygens proposed the undulatory theory in 1678: light transmitted as waves. Light waves spread in different directions from a light source, and the retina detected their vibrations.

In contrast, Isaac Newton favoured the corpuscular theory: Light as...


230 reads

Diffraction - the slight bending of light

Diffraction was first seen by Francesco Grimaldi in the mid-17 Century. When he shined a light through a small aperture, then passed it through a second aperture onto a screen, the spot of light on the screen was a bit bigger than the second aperture and had coloured fringes....


137 reads

Leonardo da Vinci's ideas on light and vision

Leonardo da Vinci's ideas on light and vision

Leonardo da Vinci thought the eye is a camera obscura into which light rays penetrate through the pupil and project an inverted image on the back of the eye. 

This idea became the dominant model of human vision in the 17th Century.


343 reads



  • In 1905, Einstein proposed returning to Newton's corpuscular theory in a modern form. Instead of corpuscles, there were now light 'quanta' (or photons.)
  • In 1900, Max Planck proposed that the electromagnetic spectra from red-hot items could be explained only if radiat...


161 reads

Understanding light through the particle and wave theory

Understanding light through the particle and wave theory

Light does not appear to bend. Sound can go through crooked pipes, but light is not known to follow crooked bends. However, when light passes through water, the angels of incidence and refraction differ.

  • Newton proposed that light's velocity in water w...


158 reads

Explaining different colours in light

Explaining different colours in light

Michael Faraday showed the inter-relationship of electric and magnetic fields of force. James Clerk Maxwell took Faraday's fields and combined them mathematically into a single concept: an electromagnetic wave with transverse electric and magnetic components that would move through the e...


116 reads


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