UV reflective surfaces Do surfaces that reflect visible light efficiently also reflect UV light?  If not, are there surfaces that do?  
(I have a large array of UV LEDs that I need to make larger and more diffuse, so I'm considering reflecting it off nearby surfaces and into some diffuse material.)
 A: Aluminium is about the best coating for mirrors below 400nm. 
Most commercial small mirrors for makeup etc will be aluminium behind glass. Although the glass isn't very good in the UV it's thin enough not to have too much absorption
A: In physics, the reflectivity of a surface is described by Fresnel Equations. One of the parameters of this equations is the refractive index which in general depends on the wavelength of light used. So surfaces that reflect visible light need not be good reflectors in another wavelength. A very good example of this is the phosphorescent coating that you find inside fluorescent lights. These coatings reflect visible light very efficiently (hence appear white to our eyes). But they absorb UV and re-emit it as visible light (this is essentially what happens when you switch the light on).
A: Most of materials that highly reflect the visible spectrum of light are highly absorbing materials for UV- spectrum, like noble metals(Au, Ag and Cu), and also alkali metals.  To have a mirror that reflect light in a long spectrum we can use multilayer mirrors that have constructed from complex of several different layers with thickness of several nanometers,(coated on a substrate) that known as VUV-UV Mirrors .
You can search for “multilayer uv mirrors:pdf” in net to find something like this:
Design of multilayer extreme-ultraviolet mirrors for enhanced reflectivity
Whatever the range of spectrum required for reflection increases, the number of layers increase.

