# Nanotechnology/Physics

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Quantum mechanics and classical mechanics are still valid on the nanoscale - but many assumptions we are used to take for granted are no longer valid. This makes many traditional systems difficult to make on the atomic scale -if for instance you scale down a car the new relation between adhesion forces and gravity or changes in heat conduction will very likely make it perform very poorly if at all - but at the same time a wealth of other new possibilities open up!
Scaling laws can be used to determine how the physical properties vary as the dimensions are changed. At some point the scaling law no longer can be applied because the assumptions behind it become invalid at some large or small scale.
So, scaling is one thing - the end of scaling another, and surfaces a third! For instance at some point the idealized classical point of view on a system being downscaled will need quantum mechanics to describe what's going on in a proper way, but as the scale is decreased the system might also be very different because the interaction at the surface becomes very significant compared to the bulk.
This part will try to give an overview of these effects.

# Scaling laws

Scaling laws can be used to describe how the physical properties of a system change as the dimensions are changed.

# Quantized Nano Systems

Quantum wires are examples of nanosystems where the quantum effects become very important.
Break junctions is another example.
Resources
* Simple model of conduction - the classical case

# Bulk matter and the end of bulk: surfaces

* Surface states are electronic states on the surface of a material, which can have radically different properties than the underlying bulk material. For instance, a semiconductor can have superconducting surface states.
* Surface reconstruction
The surface of a material can be very different from the bulk because the surface atoms rearrange themselves to lower their energy rather than stay in the bulk lattice and have dangling bonds extending into space where there is no more material. Atoms from the surroundings will easily bind to such surfaces and for example for silicon, more than 2000 surface reconstructions have been found, depending on what additional atoms and conditions are present.
* Surface plasmons
Plasmons are collective oscillations of the electrons in matter, and the electrons on the surfaces can also make local plasmons that propagate on the surface.

# The Tyndall Effect

The Tyndall Effect is caused by reflection of light off of small particles such as dust or mist. This is also seen off of dust when sunlight comes through windows and clouds or when headlight beams go through fog. The Tyndall Effect can only be seen through colloidal suspensions. A colloid is a substance that consists of particles dispersed throughout another substance, which are too small for resolution with an ordinary light microscope but are incapable of passing through a semi permeable membrane. The Tyndall Effect is most easily visible through liquid using a laser pointer. The Tyndall Effect is named after its discoverer, the 19th-century British physicist John Tyndall.

# References

See also notes on editing this book about how to add references Nanotechnology/About#How_to_contribute.
* ↑ “Tyndall Effect.” Silver Lighting. 1 June 2008. http://silver-lightning.com/tyndall/
* ↑ Davies, Paul. The Tyndall Effect. 1 June 2008. http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html
* ↑ SonneNebel. 1 July 2008. http://upload.wikimedia.org/wikipedia/commons/f/f6/SonneNebel.jpg
* ↑ Bright Flashlight. 1 July 2008. http://www.geekologie.com/2008/02/04/bright-flashlight.jpg
* ↑ “The Tyndall Effect.” http://www.chm.bris.ac.uk/webprojects2002/pdavies/Tyndall.html
* ↑ “Colloid.” 3 June 2008. http://www.merriam-webster.com/dictionary/colloid