# Refraction in Newton's Corpuscular Theory of Light [duplicate]

Newton's theory of light stated that a light travelled in a straight line as small particles. When these particles travelled in a medium, they experienced an attractive force with the particles of the surrounding medium. This attractive force was equal in all directions, and hence the particle travelled in a straight line. He extended this to explain refraction by saying that when light entered a denser medium, the particles would experience differing levels of attractive forces, as the denser medium would have more particles. This would lead it to bend towards/away from the normal.

However, in this case, how did he explain why different colours of light refracted at different angles?

• Hi, welcome! Please provide references which substantiate your description of Newton's views on propagation of light. – Carl Witthoft May 7 '19 at 13:06
• There is a 37 paged article in the History of Archives of Exact Sciences which deals with your question. Keep in mind that Netwon was not the first one to see refraction. Snell's law already existed. Newton's search for a mechanistic model of colour dispersion: A suggested interpretation (Here is the link link.springer.com/article/10.1007%2FBF00357436?LI=true) – M. Farooq May 7 '19 at 21:02
• In a developed form, Newton's theory was not corpuscular, it was a hybrid of corpuscular and wave optics. His corpuscles had vibration modes ("fits"), upon which the colors and refraction coefficients depended, and interacted with the surrounding ether. This is how he explained the interference rings as well. – Conifold May 7 '19 at 21:27
• See Isaac Newton, A new theory of light and colours (1671) : "THE THEORY [...] (2) A given colour always has the same degree of refractability, and a given degree of refractability always goes with the same colour. [...] (5) So there are two sorts of colours: original and simple colours and colours made by compounding these. The original or primary colours are red, yellow, green, blue, and a violet-purple, together with orange, indigo, and an indefinite variety of intermediate shades." – Mauro ALLEGRANZA May 8 '19 at 9:43