• Perhaps inspired by Harry Potter’s invisibility cloak, scientists have recently developed several ways,some simple and some involving new technologies to hide objects from view.
•There’ve been many high tech approaches to cloaking and the basic idea behind these is to take light and have it pass around something as if it isn’t there, often using high-tech or exotic materials.
•Many cloaking designs work fine when you look at an object straight on, but if you move your viewpoint even a little, the object becomes visible.
•Cloaking devices can also cause the background to shift drastically, making it obvious that the cloaking device is present.
•The first examples only worked with long wavelength radiation such as microwaves.
•To achieve the feat of cloaking an object, scientists have developed what are known as metamaterials, some of which can bend electromagnetic radiation, such as light, around an object, giving the appearance that it isn’t there at all.
Metamaterials
•Such invisibility cloaks rely on metamaterials, which are a class of material engineered to produce properties that don’t occur naturally.
•Light is electromagnetic radiation, made up of perpendicular vibrations of electric and magnetic fields. Natural materials usually only affect the electric component.But metamaterials can affect the magnetic component too, expanding the range of interactions that are possible.
•The metamaterials used in attempts to make invisibility cloaks are made up of a lattice with the spacing between elements less than the wavelength of the light.
Superlens
•Another use for metamaterials, potentially with greater scientific applications, is in building a superlens.
•A metamaterial with a negative refractive index might get around problems such as wave decay and allow imaging of objects only nanometers in size.
•Among the first practical applications would likely be using metamaterial lenses to view live viruses and maybe even bits of DNA.
The Rochester Cloak
•The latest effort, developed at the University of Rochester, not only overcomes some of the limitations of previous devices, but it uses inexpensive, readily available materials in a novel configuration.
•In order to both cloak an object and leave the background undisturbed, the researchers determined the lens type and power needed, as well as the precise distance to separate the four lenses.
•The Rochester Cloak can be scaled up as large as the size of the lenses, allowing fairly large objects to be cloaked. And, unlike some other devices, it’s broadband so it works for the whole visible spectrum of light, rather than only for specific frequencies.
•This cloak bends light and sends it through the center of the device, so the on-axis region cannot be blocked or cloaked.
Video : The Rochester Cloak
Applications
•Using cloaking to effectively let a surgeon look through his hands to what he is actually operating on.
•The same principles could be applied to a truck to allow drivers to see through blind spots on their vehicles.
•It can be used for surgery, in the military, in interior design, art etc.
References : physics.org ; phys.org
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