Is light a wave or a particle?

Look down on the table what do you see? some object lying on the table. Suppose, it’s a red book lying on the desk your eyes and then your brain collect all kinds of information about the book. This information will consist of its the size, colour distance etc. But how exactly does it happen well this is the combined result of the light and the eyes. In this article, We will talk about the light part of it which plays an important role in supporting our sight.

The story of how light came to light is as follows :

The ancient Greeks were the first to think more or less scientifically about “what is light?” and “how do we see?” or “how vision works?” Some Greek scientist including Pythagoras and Plato though light originated in our the eyes. Imagine how it would have been if light really originated in our eyes.They thought that some little invisible things were possibly sent to gather information about far away objects.

It took over a thousand years before the Arab scientist Alhazen figured out that the old Greek theory of light couldn’t be right. In Alhazen picture, your eyes don’t send out invisible intelligence gathering things Infact they don’t send out anything. They simply collect the light that falls on the eyes. Alhazen theory accounts for the fact the greeks couldn’t easily explain. The question that came to his mind was, “Why it gets dark sometime?” simple question isn’t it. The idea is that very few objects actually emit their own light. The special light emitting objects like the sun or a light bulb are known as sources of light, most of the things we see for example the object on your desk is the sub-sources of light. This is because they are simply reflecting light from a source rather than producing their own.

Theory of Alhazen what really happens is…

So when your look at your pencil the light that hits your eye actually originated in the sun. After which it travels millions of miles across empty space before bouncing off the pencil and into your eyes. Well, it is pretty cool when you think about it. But there were some drawbacks to this theory.

Newton to backup Alhazen:

What exactly is the stuff that’s emitted from the sun? and how do we see it? Is it a particle like atoms ? or is it wave-like ripples on the surface of a pond/ lake. Scientists in the modern era spend a couple of hundred years figuring out the answer to these questions. Issac Newton was one of the earliest. Newton believed that light is made up of tiny atom-like particles made of corpuscles.

The discoveries that followed:

He was able to explain some properties of light, for example, refraction of light. In refraction, he explained that light appears to bend as it passes from air into water. But, in science, even geniuses get some things wrong 🙂

In the nineteenth century long after newton died scientists did a series of experiments. These experiments clearly showed  that light can’t be made up of the tiny atom-like particles, for one thing, two beams of light that cross paths but don’t interact with each other at all. If light were made of tiny sand balls like thing, then you would expect the particles of beam A  would crash into some of the particles of beam B. If that happened the two particles involved in the collision would bounce off in the random direction. But that doesn’t happen, the beams of light pass right through each other as you can check for yourself taking two laser beams pointers and some chalk duster.

For another reason, light makes interference patterns. Interference patterns are the complicated undulations that happen when two waves  patterns occupy the same space. They can be seen when two objects  disturb the surface of a still pond. Also when two point-like sources of light are placed near to each other, only waves make interference patterns particles don’t. And as a bonus understanding that light acts like a wave lead naturally to the explanation of what  colouring is and when that pencil looks yellow.

In the 20th century scientists did experiments that appeared to show light acting a particle,or instance when you shine light on a metal the light transfers its energy to the atoms in the metal in discrete pacts called quanta  but we can just forget about patterns which interferes either for these quanta of light aren’t at all like the tiny hard spheres newton imagined. After Newton many scientist contributed to the theory of light and finally light was realised to be an Electromagnetic wave.

Summary:

A summary of all the contributions of different scientist view about light:

1. Light Is a Particle! (Sir Isaac Newton)
2. Light Is a Wave! (Grimaldi and Huygens)
3. Light Is Unequivocally a Wave! (Fresnel and Young)
4. Light Is a Wave – an Electromagnetic Wave! (Maxwell)

This results that light sometime behaves as particle and sometimes as wave  and this led to a revolutionary physics theory called quantum mechanics. So after this lets go back to the question what is light? light isn’t really like any thing you used to dealing with our every day lives  sometimes it behaves like a particle and other times it behave like a wave but it isn’t exactly like either. So now that your concepts on light are clear why don’t you try and study physics chapters on light and give some tests to improve your score only with Embibe.