Hellow ~

I have a question about Optics....
Can I coat a multi-fillm which has different reflection in both sides.
ie., light of specific wavelength can transmit the multi-film from one
side(low reflection) but it can't transmit from another side(high
reflection).
Who to do it if it is possible ?

Best regard ~

Hi Hotdream

     Lows of optics exhibit symmetry. That means for example, that if you
are driving beind the truck and see the driver in the mirror, then driver
can see you. If you do not see the driver, driver does not see you.

This law of symmetry is universal. It applies to any system of mirror,
obviously, but it also applies to wave phenomena, and to any sequence
of coatings. If the beam (of given wavelength) will go from A to B,
it will also go from B to A.

Mathematically this is pparent from the Fermat Principle.
This is a search term and is described in many pages, e.g.:
http://www.nas.com/~kunkel/brachistochrone/fermat.htm

Basically, lights goes by the fastest path. If A from B is fastest, then
the B to A is fastest as well.

Notice that 'fast' depends on wavelength, polarisation etc and applies to
the design of arbitrary multilayer coatings.

While principle is universal, (similar to symmetry in mechanics)
 it is not absolute.
For example, TV camera can see you, but but not the other way.
Also, if there is a difference in background illumination, human 
eye may percieve a difference in visibility. This is a subjective
effect (light will still pass both ways) but quite effective in the
construction of (so called) one way mirrors:
http://www.howstuffworks.com/question421.htm
or here:
http://www.physlink.com/Education/AskExperts/ae293.cfm

 So, answer is NO. There is no clever coating which would do that.
 However, there are situations when Fermat's symmetry will not 
be applicable.

Hedgie