First, what reflects the light, whether it is UV, visible or IR wavelength, is the metal tfab-SYTM-s5nscr22n-sketch-bluecoating on the mirror. Aluminum is a good reflector of UV, visible and IR light. However, if the aluminum is on the Back Side of a piece of glass, the glass will absorb most of the UV light and therefore, No, a back-face mirror will not reflect much of the UV light. Unless the glass is special glass that has a a high transmissivity for UV. If the mirror is front-face coated (merely polished aluminum), then yes, it should do a good job in reflecting the UV light. The reflectivity of various metals is indicated here:Page on www.layertec.de  (Source)