Hello everyone, it's been quite a long time since i presented a post like this. As we may have noticed, i have been presenting us with reports from the scientific and technological world. We would still continue with the reports though but in this post, I would love to discuss about something very fascinating of which most of us may not be aware of and it's about invisibility.
What do you understand by being invisible ?
It's simply not being able to be seen, some of us make the mistake of thinking that if you are invisible, then you're also untouchable - like a ghost. Well, that's not totally true. We basically have five senses that helps us interact with our environment and invisibility falls under one of these senses and it's the sense of sight. If the sense of sight is "apparently" lost, then other senses could help detect the object we apparently cannot see.
The most popular kind of invisibility is the kind we see in movies (fantasy or sci-fi) where the object/person appears transparent - actually more transparent than glass. You can see through the object/person like they didn't exist - see the guy in the suit, in the image above.
But is such ability possible in real life ?
Most likely, in fact, there have been experiments designed to demonstrate it but......we are still far away from showing true invisibility, those experiments have limits which depends on factors like size, wavelength and kind of wave. So, how is it possible to make an object become invisible ?
Before we proceed, let's first understand our everyday experiences of interactions between light and matter.
When light falls on an object, three things are generally possible and they are
- The light gets almost totally absorbed, with very little reflection or re-emission. Here, the object appears black. This object can be considered invisible if it's in a black environment/background - see diagram below.
- The light gets reflected/bounces back scattered (mostly), this is mostly an opaque non-black object. This is how we observe non-black objects with our eyes in the presence of external light - see diagram below.
- The light mostly passes through the object - transparency, glass is an example (keep in mind that we can still detect glass with our eyes due to the little reflections) - see diagram below.
Invisibility can be achieved in different ways, one way is having possibility (2) behaving like possibility (1) - preventing the reflected light from reaching the observer. This kind actually works well for other kinds of electromagnetic waves not visible light, for visible light the background/environment would need to be black/dark and the object small.
In movies involving invisibility, possibility (2) can become possibility (3) - opaque object appearing almost perfectly transparent. This kind is called the true invisibility, regardless of background/environment, you can't detect the object through visible light and to achieve it, visible light needs to bend in such a way that the object appears transparent. The diagram below demonstrates it.
From the diagram, external light is supposed to fall on the object and bounce back for the observer (A) to see it - as in the case of possibility (2), instead the light bends when it gets closer to the opaque object (B) and ends up at the back of the object, later unbends and continue it's journey past the object. In this scenario the observer (C) can see objects at the back of the opaque object which happens to be where observer (A) exists, in other words, Observer (C) can see through the object (B).
This approach looks more appealing and exciting but it is very difficult to implement in real life which is due to a lot of factors, though the bending and unbending can be possible. One limiting factor is that white light has multiple wavelengths which can undergo different bending and this could distort the resulting image, an observer can still be able to detect the object we are trying to hide through this distortion. This approach works well for light with a particular type of wavelength and unfortunately, the light from our sun has multiple wavelengths. 😂
Another important thing to note is that an object cannot be made invisible directly as this may require destroying the object, instead the object has to be covered with a special kind of material (sometimes called a cloak) that can manipulate the propagation of light to give the invisibility. Those special materials belong to what is now known as "metamaterials". Metamaterials are materials that have artificially designed structures (depending on the wavelength of the wave in question) that helps manipulate the wave to get a desired result that is otherwise not observed in those materials without the artificial structures.
It is suggested that a combination of metamaterials and metalenses could help resolve the issues of the distortions discussed earlier and other problems but in truth, there's more research needed to be done to achieve true and practical invisibility and I guess only time would tell.
I wonder how two different invisible groups of soldiers would cope in a battle against each other. 🤔
Maybe heat signature sensing could do the trick. 😂😂
References
Invisibility cloaks are not just possible, but are becoming reality
Engineered Metamaterials Can Trick Light and Sound into Mind-Bending Behavior
It is here we conclude today's article, have a thoughtful day and till i come your way again next week.
Thank you all once again for stopping by to read my jargons and also thank you 
Lastly, please don't forget to do the needful
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