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# Light is What You're Seeing

Updated: Jun 27, 2021

By Miraya Kwatra

It’s impossible to have an enmity with light. In a way, light is essential for survival, without which you’ll be enclosed in the dark forever and be practically blind.

UNDECIDED LIGHT AND ITS CONSTITUENTS

Light can be defined as something that can reflect, refract and diffract. For instance, you’re sitting in your room, studying. Your mother comes in and puts a brand new hard - cover novel on your desk. Now, how are you able to read whatever is written on it? In simple language, the light of your room is falling on the book, and the book is sending those light rays into your eyes.

Components, structure and form. Light is energy, a form really. Research and several reasoning theories questioning, “ Is light made of waves or is it a substance containing particles?” ,have brought up conclusions that it is, in fact, both. To prove anything related to light, reflection, refraction and diffraction play a vital role. Diffraction is the spreading of light through a convex mirror.

Newton stated that light consisted of a straight line of particles, which he also called corpuscles. (a small unit related to basic matter and light) Although this theory explained why light divides into seven different colours when reflected on to a prism, it wasn’t quite able to answer the question about light showing a little refraction and sometimes reflection when beamed onto a surface. When light is beamed onto a plane mirror, it bounces off in straight lines: which, as you would’ve guessed, goes well with Newton’s “particle” theory.

If light is a wave, then, according to its reasoning, the reflected substance would be spherical, which isn’t true. Though, when reflected from a distance, it does show semi- linear formations. Refraction can be simplified as a term used for the bending property of light. Light bends when it’s transmitted through two optical materials. We’ll ponder and reflect more on this topic in the next section.

If you’ve ever observed the sea closely, you would know what we broadly mean by light being a wave. Aether, is a substance that isn’t actually visible but its part in the wave theory, would perhaps make you regard it as wonderful. Even if you are well knowledgeable in space and cosmos, aether, despite being a prominent substance in the universe, would still be a matter of deep research and it will most certainly fascinate you. Huygens stated that light travelled through aether and when it did, it turned into a wave, implying that aether too has wave-like characteristics. In the case of waves, he said that aether shows a movement in the same line of propagation as light and in a way changes the nature of light, in a similar way to light.

At this point we naturally bring ourselves to Snell’s laws of refraction. In relation to waves, we need to lay emphasis on refractive indices. A refractive index is, in simple terms, a measure and when light goes past it, it changes its form according to that measure.

Research has shown possibilities that are great to dive into so prepare yourself for a journey with light in its world. When light travels from one medium to another, it also changes its direction. For a moment consider light to be a wave. Now visualise this. A ray of light is travelling from the air to an open bottle of water. Divide the ray into two parts. This way one the bottom half reaches the water, the upper half would still be suspended in the air. Because the refractive indices of both the materials are different the light will bend and change its speed, causing the way you see it to change..

The sea’s waves hit the rocks, which stop them from crossing the rocks. But, when an object is kept in the way of light, it doesn't stop at the interference, instead it transmits beyond it. Now, think of the interference in the form of a leather chair. The light won’t pass through it, instead it’ll create a shadow, pin pointedly at its bottom. Particles are small molecules creating a straight line but waves of light would curve and bend, when stopped. This concludes the fact that light is indeed “undecided”.

Just with a touch, you switch on and switch off a power of the universe and that being said, a power of yourself. But light is much more than that, way more. Ever heard of the term “electromagnet”? You must have heard of the deflection of a piece of magnet when it’s in close proximity to an electric medium, introduced by Hans Christian Oersted. To extend what Micheal Faraday believed, he said that light was a combination of electricity and magnetism.

Here’s how he worked it out. Light polarization means the periodic movement of light in one direction. Let’s substitute, bit by bit, Faraday’s experiment through an example. For instance, a slab of plane mirror is kept vertically on a table. You’re pointing a torch toward it, in the presence of a large magnet. The beam of light is getting reflected at some angle. When you move the magnet, the angle of the ray would change.

THE MOVEMENT OF LIGHT : LENSES AND MIRRORS

In the first section, we talked about refractive indices and came across the term Snell’s laws. Reflective telescopes use mirrors in their eye piece. Mirrors reflect the light while lenses refract it. The basic properties of concave and convex lenses and mirrors are something everyone is aware of. But how these properties work with light is what we’re yet to see. Concave mirrors and convex lenses have similar traits and so do convex mirrors and concave lenses. A convex lens converges the light, that is, the light rays meet at a single point. There is a theoretical and practical reason behind this. The axis of such a lens is the host for the light rays that enter it, somewhat equidistantly. They go in from one side and while exiting meet at a centre known as the “focal point”. Because of the refractive index of the lens and the first material, light is bent in such a way. The working of a refractor telescope is based on its convex lens. The light comes in and the beams adjoin and intersect at the opposite side of the lens, creating an excellent and clear image of the celestial body that is being viewed. The power of the lens is the inverse of its focal length. For example, the focal length of a lens in 15 metres, its power would be 1/focal length. Which is, 1/15 = 0.067 Diopters (approx.). The images formed by convex lenses are big in size and they’re real and inverted.

Now that you have an idea as to what the different components of lenses are, let’s come to concave lenses. In contrast to convex ones, they’re called diverging lenses, the meaning of which was pointed out in the previous section. When a concave lens comes in contact with light, the rays spread out from the opposite direction, at the focal point. When rays travel through the lens with the axis, their focal point and length are pushed back. On the other side, they’ll not be parallel, well, it’s a concave lens. The focal point is, instead, considered to be where the light starts to enter. And, so, the focal length and the power of the lens are taken in negative.

Mirrors too, have many ways and paths. We’re going to talk about two of them in this article, convex mirrors and concave mirrors. The more the mirror is curved, the measure of its radius will decrease. If the curve is big, it won’t be able to provide an exact focal point and length. Concave mirrors are converging. The light ray, upon falling on such mirrors, reflects back, making the image magnified. Assumption of measures and positions is necessary when talking about mirrors. Note that mirrors are painted on either of the sides, implying the needs ( whether it has to be plane, convex or concave etc.). Convex mirrors have their focal point, focal length and power in negative, just like concave lenses. Although there is nothing at the back of convex mirrors, we imagine the focal point to be created there, because the light, again, is getting reflected. They throw out the light on the same side and don’t let the beams cross. There is a way, by which the focal point of mirrors can be almost accurate, when they’re too big compared to the radius of the whole sphere. If they’ll be less curved, then the circle would become bigger. These kinds of mirrors are called parabolic. Concave mirrors are used in reflector telescopes.

A parabolic mirror. Notice the focal point.

These were just a few of many deep and brilliant concepts of light. I would most certainly call it infinite!

REFERENCES:

## Beléndez,A. (n.d) Faraday and the electromagnet theory of light https://www.bbvaopenmind.com/

Image formation by lenses (n.d) https://courses.lumenlearning.com/

Image formation by mirrors (n.d) https://courses.lumenlearning.com/

IMAGES:

IMAGE 1: T.Sutter, R. Parry-Hill, M. (n.d) https://www.olympus-lifescience.com/

IMAGE 2:

T.Sutter, R. Parry-Hill, M. W.Davidson,M (n.d) https://www.olympus-lifescience.com/

IMAGE 3:

Image formation by lenses (n.d) https://courses.lumenlearning.com/

IMAGE 4:

Image formation by mirrors (n.d) https://courses.lumenlearning.com/

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