Can We Make Harry Potter Invisible?? Harry: Invisible Man Intro (0.5) Video (1.5) - 2 Harry: Invisible Man Is Invisibility Possible? Dr Behan

Is invisibility possible? Video (1.5) – 2.5 ?Invisibility? Is Invisibility Possible? Dr Behan

How it works A digital video camera captures the scene. A computer processes the captured image. A projector receives the enhanced image and shines an projected image toward the person wearing the cloak. The cloak acts like a movie screen, reflecting light directly back. How it works Explanation (1) - 3.5 Is Invisibility Possible? Dr Behan

Possible improvements Is this any use? Camera Tripod? Bad points Only works in 2D Shows some reflection Not very dynamic! Good points Results that work Possible improvements Inexpensive Explanation (2) - 5.5 Bit of a cheat really!! Is Invisibility Possible? Dr Behan

A wave of energy, made up of different wavelengths. What is Light? A wave of energy, made up of different wavelengths. Glasses (1) Talk (2) - 11.5 See for yourselves!! Is Invisibility Possible? Dr Behan

How does light interact with objects? Natural form of invisibility is an object which neither reflects nor absorbs light (it allows light to pass through it). Absorption - Occurs when electrons absorb light energy Reflection - Occurs strongly in smooth, conducting metals with free electrons Talk (2) - 13.5 Transmission - Occurs strongly when there are large enough gaps between atoms for the light to pass. Is Invisibility Possible? Dr Behan

Does invisibility exist in nature? Trick (2) Talk (1) - 8.5 Is Invisibility Possible? Dr Behan

Secret of the sky practical Pour water into tank Shine the flashlight beam through the tank as shown in the diagram. Hold white paper in the two places shown on the diagram and record what light you see. Add a pinch of powdered milk and then stir. Repeat the previous step.

So why is the sky red/orange at sunset?

Are there any invisible materials? Crystals Highly organised “crystaline” structure Exist in crystal planes which light can travel between Man made transparent solids Plastics Glass Boiled Sweets! Talk (2) - 15.5 Is Invisibility Possible? Dr Behan

How do we make glass transparent? Glass is made from sand! Heat to a liquid Made from sand (silica) Cool to glass Talk (2) - 17.5 Glass has strong/rigid bonds like a solid but… An irregular particle structure like a liquid thus allows light to pass Is Invisibility Possible? Dr Behan

Not without killing him!! Can we use this to make Harry invisible? Not without killing him!! Talk (0.5) - 18 Is Invisibility Possible? Dr Behan

A different approach Talk (1.5) Trick (2) – 21.5 Is Invisibility Possible? Dr Behan

The denser the material the “slower” it goes. Can we bend light? Yes - Refraction!! Air Glass Talk (2) Demonstration (6) – 29.5 When light passes through a material it slows as it has to pass trillions of atoms. The denser the material the “slower” it goes. Is Invisibility Possible? Dr Behan

Reappearing coin trick 1. Put a penny in a cup. Look at the penny, then walk backwards until just after you can't see the penny anymore. 2. It's very important that you can't see the penny. Without that, the magic of this trick fizzles into nothing. 3. Stay where you are, and have your friend pour water into the bowl. 4. If all goes well, the penny should appear.

Why do the stars twinkle?

Refraction Refraction

So, can we make a cylindrical cloak? American news 1 mm Ametamaterial made at Durham, North Carolina and Imperial College made an object invisible to microwave radiation. Talk (1) Video (2)– 35 http://Duke University cloak Is Invisibility Possible? Dr Behan

Steps to success Invisibility for all wavelengths in 3D David Smith Duke University “A true invisibility cloak IS possible within the laws of physics. With good research it should be a matter of time” Steps to success Invisibility for all wavelengths in 3D (Unclear solution based upon layers) Invisibility for all wavelengths in 2D (Requires complex stacking of wafers) Talk (1)– 43 Invisibility for one wavelength in 2D (Requires sophisticated patterns to bend light smoothly) Is Invisibility Possible? Dr Behan

Differences compared with Harry’s cloak Need flexible metamaterials. This would be a rigid, most likely cylindrical, device. A spy hole would mean floating eyes. Seeing out of any such device would be a problem. Talk (1)– 44 Is Invisibility Possible? Dr Behan

What are the uses for an invisibility cloak? Police Army Hiding Eyesores Fashion Talk (3)– 47 Stealing Spy on people Is Invisibility Possible? Dr Behan