Scientific Sunday#3- Light

Light

Last week I mentioned that I will be writing about light waves…. or was it particles? There has been a prolonged argument whether light should be and behave like a wave (like sound waves which I wrote about last week) or a particle (made up of small particles and behaving like one). Anyway, today I will try my very best to explain the nature of light: of how they behave, and the secrets behind them.

The mysterious Light

Light, according to Einstein, is the fastest thing in the entire universe. Moving at a mind-blowing speed of: 299,792,458 meters per SECOND!!! Around A MILLION times faster than the speed of sound!!! But still, it has a speed limit, it is not infinite. The universe is BIG, a lot bigger than you think. For example, the distance from Earth to the Sun is about 149,600,000 km, it takes around 8 minutes for light to travel that distance. In other words, the sunlight you are feeling now(only if you are reading this during day time...) left the Sun 8 minutes ago!

Light also consists of every colour possible, proven in the Newtonian prism experiment. Basically, if you shine a beam of light into a glass prism, you could see( although barely ) all the colours of the rainbow coming out of the other end. If you intercept the colours with a convex lens and another glass prism, it will come out with the original light again. 

Light, is also the reason why we can see things. Everything we see is a reflection of light, if it's a blue colour, it will absorb every other colour and reflect blue, red reflects red light, black absorbs every colour, white reflects every colour and so on...... That's the reason why when you are in a room with no light shining or coming from outside, you will not be able to see anything because there is no light reflecting!

LET THERE BE LIGHT!

A prism 

Isaac Newton VS. Rene Descartes

After the success on his theory, Newton published a new theory that light is made up of particles, instead of waves like sound. The theory was rapidly accepted. But scientist Rene Descartes said otherwise, he published a theory of light being wave-like, contrary to Newton. Rene Descartes didn't have strong evidence to prove his theory right, not until Dutch astronomer- Christiaan Huygens and Thomas Young corroborated it in the near future. Christiaan Huygens gave the reason: Two beams of light could cross over each other without being affected by one another, if light was made up of  particles, the beams would inevitably collide and bounce away from each other in all directions, but it didn't. Shortly later, the people's opinion slowly swung across to this theory.

In the early 1800s, Thomas young further enhanced it with the Double slit experiment. The experiment showed interference of light waves diffracting after passing through a panel with one slit followed by another panel with two slits and at the end onto a covered panel, which showed the pattern of interference. The result of this experiment certainly proved that light does in fact behave more like waves than particles.

But it doesn't mean that Newton was completely wrong, because in the 20th century, Einstein and Planck showed that light could act as both particles and waves. The quanta of electromagnetic radiation they recognized later became known as photons.

The Double split experiment

The full diagram

Finally, light is complicated but at the same time interesting, without light we certainly could not survive.

That's it for today, I will see you next week.

Thanks For Reading