V I S I B I L I T Y

• It is a measure of the distance at which an object or light can be clearly discerned

• REASONS FOR VISIBILITY:• When light gets reflected from the object, the reflected light enters our

eye retina and thus we are able see that particular object from which light was reflected from.

• In our daily life, we see certain things which are transparent, they appear transparent because most of the light is refracted instead of getting reflected.

CAN WE CREATE INVISIBLE THINGS• Invisibility is the state of an object that cannot be seen. • Creating something perfectly invisible obviously means that it reflects no

light and every light ray passes through it. If it would absorb all the light, then it could be easily distinguished from its background. So there are kind of 3 possibilities

• You create something that blends and camouflages in the background• You create a smart object that detects its surroundings and if a light ray

touches it, it absorbs it and then emits it from the other side following the path of the light.

• As already mentioned above, under certain conditions its easy to make something invisible. But to make something invisible in every surrounding would require artificial intelligence as well.

To become invisible, an object must do two things: • It has to be able to bend light around itself, so that it casts

no shadow, and it must produce no reflection. While naturally occurring materials are unable to do this, a new class of materials called metamaterials is now making it possible.

• Bending light around an object requires a material to have a negative refractive index. The refractive index is a property that dictates how light passes through a medium; it’s the reason a stick will look bent when placed in water.

• If water had a negative refractive index, it would make the stick look as though it were bending back on itself.

The camouflage fabric ‘ that can make soldiers INVISIBLE

Making use of a real-time image displayed on a wearable display, it is possible to create a see-through effect. This is known as active camouflage.

Technology can be used theoretically or practically to render real-world objects invisible• Stealth technology is declared to be invisible to radar, all officially

disclosed applications of the technology can only reduce the size and/or clarity of the signature detected by radar. With stealth & Without Stealth

CLOAKING

• "cloaking device" is used to make objects invisible • This is acomplished by manipulating the paths transversed by

light through a noval optical material known as metamaterials• These materials direct and control the propagation and

transmission of specified parts of the light spectrum and demonstrate the potential to render an object seemingly invisible.

• Metamaterial cloaking based on transformation optics describes the process of shielding some thing from view by controlling Electromagnetic Radiation

How to Make an Object Invisible1.Simulations show how light interacts with the cross section of the cloaking device.

2.When it’s uncloaked (top), light is reflected off the object.

3.when it’s cloaked (bottom), light is guided around the object and anything within it.

4.A hairbrush-shaped device has been theoretically designed that would use bristles made out of nanowires to bend light around it, rendering the object invisible it’s the first practical design for an “optical cloak” to work in the visible spectrum and now working on building an actual device based on their calculations.