Light
Light is generally considered as a form of energy and that is because it really is. Simple is that? No, definitely not. On the advanced level, light has not been fully understood as to how it behaves. In modern Physics, it has been proven that light is both a particle; the Photon and a wave but the problem still remains that how does it work or at what time does it behave like a wave or a particle. Experimentation has been done to prove that light is both a wave and a particle like The Double Slit Experiment.
Light is Massless but it has Momentum
What really is amazing about light is that being a particle it has no mass, meaning it is massless. And that kinda makes sense to the Einstein's Theory Of Relativity, as he had described it earlier that anything in the universe with no mass must move at the speed of light.
Although, the wave-particle duality of light has been proven but the real concern is again with its physical property of being massless. Light being massless generates some really important questions in the mind of a Physics lover like;
1-We have been studying that the laws of gravity are only and only applied to objects that have mass but it is also found that light is also affected by gravity. The gravity of a huge star can bend a ray of light or a black hole can completely trap light. So what then? Why is it going against the laws of Physics?
2-We all know that momentum is the product of Mass and Velocity but it is a fact that light has also gotten momentum too. Then, How can it have momentum at the same time it does not have any mass?
3-Having momentum will surely mean the conservation of energy and that is why light should be applying a force on any object it hits. Yes, it does but how much?
There are tons of other questions but these are the most important and widely asked questions. Many great Physicists have tried to answer them and yes, their answers are quite convincing. Over the years, I have collected their answers and have done my personal research. But for your convenience, I would just list them below in points.
1-According to the laws of universal gravitation, only the objects that have mass must experience the force of gravity. As light does not have any mass in the first place, so it must not be gravitationally attracted but there is more to it and that is Energy. Light is Energy, and according to the famous equation of Einstein, the E=mc2, energy is Mass. So that is why its energy sort of act like its mass and thus makes it gravitationally attracted to celestial bodies.
2-The question of light having momentum although having no mass is also answered by it having energy. Actually, modern Physics say that momentum is not actually the product of Mass and Velocity, it is more accurate to say that Momentum is the product of Energy and Velocity. Hence light has energy and velocity, so it surely has momentum.
3-Light has momentum and can push things away that comes in its way but with very very little force. The Photons or the light particles are massless and they need a tiny amount of energy to reach the ultimate speed or the universal speed limit which makes light the fastest thing in the universe.
OK, it is pretty much clear now that light is energy, it has momentum and works both as a particle and a wave at the same time but how to prove it. For this, I have gotten a simple experiment that can be done easily at home and it is the Double Slit Experiment.
I am writing the procedure to conduct this experiment in points.
1-Take a box and make two very small slits close to each other.
2-Make a hole just above the slits which will work as an eyepiece so you could see what is making up inside.
3-Adjust a light source, more preferably a laser and shine it straight onto the two slits.
After you have peered inside the box, you record your observation and then tell me in the comments section what you saw. Thanks for reading and have an amazing day.
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