During the later part of his life Newton got caught up in a very big debate… is light a particle or a wave.
Newton believed very strongly that it was aparticle, and given that he was such an important scientist many people thought he was right.
Remember, he was the President of the Royal Society, so if he said something was true, many other scientistswould just automatically agree.
On the other side of the argument you had people like Christian Huygens, who although he was basically unknown, had a lot of carefully thought out physics to back up hisclaims that light was a wave.
Sadly, Huygens had a hard time getting scientists to listen to his ideas simply because they were the opposite of what Newton was saying.
Light is a Particle?Newton did have several pieces of evidence that light was a particle:
Light travels in straight lines. If light is a particle then it will not be able to diffract after going through an opening oraround an obstacle. Particles always move in straight lines, and light seems to move in straight lines. (N.B. This is not the same as refraction, which is when a particle or wave changes direction aftergoing from one medium to another medium.)
Light can travel through a vacuum. In Newton's time, the only waves that anybody really knew much about were mechanical waves, which need a substance (amedium) to move through (e.g. sound travels through air). Since they also had a pretty good idea in Newton's time that the space between the earth and the sun was a vacuum, how could light reach earth if itwas a wave? If light is a particle it would have no trouble moving through a vacuum.
Light is a Wave?
Huygens had a tough job, since not only does he have to disprove Newton’s two main points, healso has to overcome the power that Newton has in the world of science.
Huygens focused most of his attack on the first point outlined above.
If he could show that light would diffract when...