1) Cloaking technology uses metamaterials to bend electromagnetic waves like light around objects to make them partially or wholly invisible. 2) An invisibility cloak system works by using a digital camera to capture the scene behind the wearer, processing the image, and projecting it through the cloak material to create the illusion that only the background is visible. 3) Acoustic cloaking aims to guide sound waves around an object using a cylindrical structure of concentric rings with varying acoustic properties, aiming to cloak objects from sound detection.

1. INVISIBLE CLOAKING
T SRIRAM REDDY

2. Cloaking is a technology that can cause objects to be
partially or wholly invisible to parts of
the electromagnetic (EM) spectrum.
According to Fermat’s Principle, light follows the
trajectory of the shortest optical path, that is, the path
over which the integral of the refractive index function
is minimal. Therefore, the refractive index of an optical
medium determines how light propagates within it.
Consequently, by a suitable choice of refractive index
profile for an optical medium, light rays can be bent
around and made to propagate in closed loops.
INTRODUCTION

5. It can make the light bend in an opposite direction from
normal paths.
It is made up of individual pieces of fiber glass arranged
in parallel rows.
These hollow fibers are motels of photons –light checks
in, but it never checks out.
The arrangement of it enables the cloak to deflect or
bend the light making it appear as nothing.
METAMATERIALS

7. INVISIBILITY CLOAK SYSTEM
A digital video camera captures the scene behind the
person wearing the cloak.
The computer processes the captured image or video so
it will look realistic when it is projected.
The projector receives the enhanced image from the
computer and shines it through the opening onto the
combiner.

8. The silvered half of the mirror, bounces the projected
image toward the person wearing the cloak.
The cloak acts like a movie screen, reflecting light
directly back to the source.
Light rays bouncing off the cloak pass through the
transparent part of the mirror and fall on the user's eyes.
The person wearing the cloak appears invisible because
the background scene is being displayed onto the retro-
reflective material.

9. ACOUSTIC CLOAKING
A model for directing sound waves to go around,
instead of colliding with, an object effectively
cloaking it from detection.
The cloaking mechanism consists
of 16 concentric rings in a
cylindrical configuration, and each
ring with acoustic circuits. It is
intentionally designed to guide
sound waves, in two dimensions.

10. Each ring has a different index of refraction. This causes
sound waves to vary their speed from ring to ring.
The sound waves propagate around the outer ring,
guided by the channels in the circuits, which bend the
waves to wrap them around the outer layers of the
cloak.
The acoustic cloaking device works in all three
dimensions, no matter which direction the sound is
coming from or where the observer is located, and holds
potential for future applications such as sonar avoidance
and architectural acoustics.

12. The cloak could be used to cover volume of any shape
but moving the material would spoil the effect.
Current devices work only for narrow range of
wavelength but light has many wavelengths.
It is a slow process.
LIMITATIONS

13. APPLICATIONS
Cloaking military devices
Advanced concert halls
Stealth warships
Diagnosis
Magic, Art

14. FUTURE SCOPE
Many practical uses exist for materials that can
precisely control the paths of light, sound and harmful
radiation. There are just as many sinister applications
that come to mind for a cloaking device.
The Invisibility Cloak is another impossible product
made possible by rapidly advancing technologies and
a better understanding of our universe. It would
benefit the public to readily address the social impact
of invisibility before it materializes in real
applications.