Can things be Made Invisible? - The Mystique

Can things be Made Invisible?

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               The use of invisible cloaks can be noticed in the series of Harry Potter. It would be great to become invisible just by a cloak. But is this really possible? Do invisible cloaks be made practically? Yes, it is possible. We have developed two-dimensional invisible cloaks (thickness of order micrometers) till today. There is a better scope for developing three-dimensional invisible cloaks in the future.

                 Invisible cloaks are of two types: acoustic & light invisible cloaks. When sound is fired through the object covered with acoustic invisible cloak, you see nothing; neither cloak nor the object. The first three-dimensional acoustic invisible cloak was made possible by Duke University. It has various applications in military and architecture. Light invisible cloaks does not allow light to pass through them and hence nothing can be seen behind that. So, object can become invisible. Light invisible cloaks can be useful in manufacturing electronic devices and in architecture. Let us see a brief view of light invisible cloaks.



          Light invisible cloaks are no magic indeed they are magic of science. The working of light invisible cloaks is similar to that of mirage formation. In deserts, as the temperature is high, ground gets heated quickly. The bottom most layers of air are heated to a greater extent when compared to the layers at higher ascent. When light travels from cooler layers (top layers) of air to hotter layers (bottom layers) of air, it undergoes refraction to such an extent that light almost bends to U-shape. This is due to a large difference in temperature gradient between those layers. It appears to the viewer as if he is seeing the straight light and falls to an illusion.  When light falls on the cloak, the light is bent in such a way that it does not pass through the cloak.

     
         Invisible cloaks are made up of specially made materials called metameric materials. Metameric materials are prepared properly that they can guide light completely out of them. The alignment of atoms plays a crucial role for refracting light. Especially, negative invisible cloaks are used for making these cloaks. Negative invisible cloaks refer to the materials which have negative refractive index. All the naturally occurring substances have positive values of Permeability and Permittivity. So, refractive index is positive. But, metameric materials could be made such that they can have negative values of Permeability and Permittivity so refractive index is negative. A Microwave source is used as microwaves are not visible to naked eye.



Refractive index is given by

                                                                                                                              
          There are many applications associated with invisible cloaks. These cloaks can bring the revolution in the field of electronics. They also can be used in military and architecture. If there is excel in the development in 3 dimensional invisible cloaks, the size of gadgets can be flattened to a larger extent.

           Invisible cloaks have its pros and cons. If they are not used properly, they can lead to destruction. If they are used in a proper way, they undoubtedly stand as a mark for human excellence.

                                            

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