Many legendary minds in early time stated their point of view about light because it was the source of life and an amazing thing in the universe. Some people believed that God is the source of light and it flows from him like a fountain.
Everyone can give their suggestion but the proof for that suggestion matters the most. Newton is considered as one of the great minds among early physicists but his proposal about light was not completely true.
Light is a mysterious thing and still, we don’t understand all its properties. Light is made up of particles called photons and the major contradiction is in the motion of light. An experiment shows that light moves like a particle (Small Ball) in space. Experiments also show that light is an electromagnetic wave and it travels like a wave in the space; Sound waves are also similar waves but they are mechanical waves.
Nature of Wave
Let us see how the wave nature of light is coined. Imagine that last night there was heavy rain at your home place. The Next day morning you sneak out of our home to look around. You find some stagnant water near your home like a small pond. You throw some stones on the water and the stones create a wave on the surface of the water. That wave is small in the place where the stone is dropped and it grew big as it travels to the edge of the pond, you can notice that in the following image.
According to the Law of conservation of energy, Energy cannot be created or destroyed but only can be changed from one form to another. Here the force by throwing the stone is distributed throughout the water in the form of waves. In other words, the disturbance created by the stone is transferred in the form of a wave. This how the sound and light travels in the space. We can see how the sound wave travels in some medium but it is not possible to see the motion of light in any medium.
Light can travel without any medium and that property is another big topic. This is what a wave means and we can observe this kind of wave in our daily world in many places without knowing itself, like sea waves. A wave has a crest and trough. The upper part of the wave is known as the crest and the lower part is known as the Trough. If a Crest and trough meet each other, it will not be formed.
Young’s Double Slit experiment
The Agenda of this article is the proof of the wave nature of light and the experiment which supports the wave nature of light is Young’s Double Slit Experiment. Most of us would come across this experiment in our school days without knowing the actual purpose of the experiment.
The slit is kind of window but a very small one which allows a very small amount of light through it. The light used in this experiment is monochromatic light, which is a light with the same wavelength.
Let us go with one slit experiment first, imagine a one slit sheet is placed between the light source and wall. Once the light is turned on it produces photons and it flows through the slit and creates a bright line corresponding to the slit. This is what happens when a particle (Small Ball) and also wave is used.
Now let us go with a double-slit experiment in which the sheet has two slits and it is placed between the light source and wall. Once the light is on we can see some strange thing is happening now and if light acts like a particle (Small ball) we should see only two bright lines in the wall but that is not what we see in this experiment. We can see a pattern of dark and bright lines with a center line is brighter. This weirdness only paves way for another different field called Quantum mechanics. So why do see such a different pattern?
Wave Nature of Light
The answer is the light acts as a wave in nature. When light from the source starts it travels like a wave in the space similarly wave in water. Then it reaches the slit, again it creates another new wave while crossing the slit, so we get two different waves after the slit. As it is mentioned above the wave consist of a crest and trough, when a crust and trough meet each other it gets canceled. Hence we see the dark pattern of the lines in the wall due to this phenomenon. Eventually, when a crust and crust meet each other or trough and trough meet each other it gets doubled in size. Hence we see the bright line due to this phenomenon. The diagram clearly shows that when the light starts from the bulb it travels like a wave and again when it crosses the slit that creates another wave. The only explanation of this weirdness can be proved if we consider light has wave nature.
Twist in the Theory
This experiment was the proof of the wave nature of light but there is still no end for the research in this field. So we can’t say that light acts only as a wave in nature. Later came a hero who can prove both the particle nature (Small Ball) and also the wave nature of light by his theory.
Louis De Broglie
He states that light as both Wave property and particle nature; he called this as the duality of light.
This was the climax between the light and physicist, so De Broglie shot was notable in this event. Even-though it is in climax now, don’t be happy that the movie will end soon; These experiments are a series and this is the climax of the first episode only. still, we have many episodes to go.
A science is any discipline in which the fool of this generation can go beyond the point reached by the genius of the last generation” – Max Gluckman
Duality of light
The De Broglie Explanation was every particle in nature shows the dual property of wave and particle. Let us imagine you are in the keeper position in the cricket field and a ball is coming towards you. You see a ball is coming without any oscillation if it was launched by a good bowler. But the ball is coming with some oscillation. Deep down if you see the ball will be traveling like a wave but its oscillation is too small to predict. This explanation is known to be a renowned one in the physics world. We can learn from this that every moving object in this universe even flight, car, bullet seems to be traveling without any oscillation but under a very closed state, they do experience oscillation.
If you want to find the secrets of the universe, think in the terms of energy, frequency and vibration.
– Nikola Tesla
After this you may understand how the light is moving in space, it doesn’t mean that light is only a wave thing. Sometimes it shows particle nature also and there are many experiments to prove that. This confusion only paved the way for quantum physics, if you want to know more about Quantum physics leave a comment.