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

Scientific Sunday#2- Sound Waves

Sound Waves

Have you ever wondered how noise-canceling Headphones works, or why and how the sky of the Earth during mid-day is blue but orange red during dawn and dusk?Today I will be writing about everything I know about sound and light waves.

What is a wave?

A wave is a disturbance that transfers energy through a medium of interacting particles. This oscillating pattern carries energy from place to place without moving matter itself. There are many kind of waves- sound waves, light waves, electromagnet waves.

 Waves move energy in a ripple effect, like how the more energy and in a faster phase you transfer to a water surface, the higher and closer each wave will be.

The same principle applies to small ripples in a pond and to devastating tsunamis.

Sound wave moves in pattern similar to ripple

Noise-Cancelling Headphones

Unlike solid objects, waves- which move energy, can actually move through each other. There are two important types of results when two waves move pass each other. The first one is if two waves move in the same direction and share the same frequency, the result will be additive- a new wave that combines the amplitude of the first two, still moving in one direction, at the original frequency.

But if the waves' peaks line up, the combination will result in a new, higher wave.

On the other hand, the first wave’s peaks line up with the other’s, the two wave patterns will cancel each other out. Sounds strange right? There had been two wave patterns, but there will now be none. This is called destructive interference.

So now do you get a brief idea of how a noise-cancelling headphone works? I used to think that what it does is just to cover our ear completely and hence there will be no sound travelling into our ears. And turns out I was very wrong. The headphone's active noise control systems work by generating a sound wave that is the mirror image of the offending sound wave. This wave has the same frequency and direction but opposite crests and valleys and is out of phase with the first sound wave. The result, is minimum sound blasting into your ear.

An amazing and clever idea right? Active noise control is usually used in such application as airplane cabin, air conditioning duct, and wore by pilots, not only to cancel deafening engine noise, but also allow pilots to communicate. Can you think of other product that applies the active noise system?

Next week I will be writing about light waves, a more complicated type of wave, but I will try my best to explain how it works and why is it useful to us.

Thanks for reading