# Forum for Science, Industry and Business

Search our Site:

## Visualising invisibility

31.07.2006
Invisibility has been an ingredient of myths, novels and films for millennia – from Perseus versus Medusa in Greek legend to James Bond’s latest car and Harry Potter’s cloak. A new study published today by the Institute of Physics reveals that invisibility is closer than we think.

The paper, Notes on conformal invisibility devices, published in the New Journal of Physics (co-owned by the Institute of Physics and German Physical Society) describes the physics of several theoretical devices that could create the ultimate illusion – invisibility.

“Objects are visible because they reflect light rays” says author Dr Ulf Leonhardt at St Andrews University, Scotland. “To be invisible, an object would have to let light pass through it, like H. G. Well’s Invisible Man.

Alternatively light would have to bend around an object for it to be invisible. The ideas in this paper are based around devices that will bend light or radio waves around a hole inside the device. Any object placed inside the hole will become invisible. The light would flow round the hole like water around an obstacle.”

The bending of light is the cause of many optical illusions, such as mirages in the desert. Light bends in the hotter air near the ground in the desert and this causes a reflection of the sky on the ground – a mirage.

Dr Leonhardt went on to say “The devices work by bending light, as in a mirage. However, a mirage involves the reflection of light which produces the shiny image that can be seen: an invisibility device bends light without producing an image. To do this, the devices must have carefully designed refractive index profiles. The paper explains the physics and mathematics behind the devices using images rather than complex equations: it visualizes invisibility.”

The refractive index is a measure of the optical length that light has to travel in a medium: the higher the refractive index, the longer the optical path is to the light ray. Light rays bend when the refractive index of the medium they are travelling through varies. According to Fermat’s Principle of optical paths, light will follow the shortest optical path length. In the case of the mirage, air closer to the desert ground is hotter and has a lower refractive index than the cooler air higher up. Therefore light bends close to the desert floor in order to stay in the lower refractive index region.

Dr Leonhardt added “The next step is actually making one of these theoretical devices. There are advances being made in metamaterials that mean the first devices will probably be used for bending radar waves or the electromagnetic waves used by mobile phones. Such devices may be useful in wireless technology, for instance in protecting sensitive electronics from mobile-phone radiation in airplanes. After these have been developed, it is possible that devices that work for visible light are not too far behind.”

Helen MacBain | alfa
Further information:
http://www.iop.org
http://www.iop.org/EJ/abstract/1367-2630/8/7/118

### More articles from Physics and Astronomy:

CCNY-Yale researchers make shape shifting cell breakthrough
12.12.2018 | City College of New York

Electronic evidence of non-Fermi liquid behaviors in an iron-based superconductor
11.12.2018 | Science China Press

### Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

### Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

### Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

### Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

### Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige