What are Good Mirrors Made out Of?

Is there a material which is more reflective and suitable to be used in a mirror than silver?
- Yigit Polat (age 23)
Istanbul, Turkey

Hi YiÄŸit,

There are multiple ways to make a mirror. Many flat surfaces are reflecting, such as minerals, metals, or water. For example, your household mirror is probably made of a flat, polished layer of aluminum (or perhaps silver) covered by a protective glass coating. Higher-quality mirrors (i.e. for research or for cameras) are usually made using very thin layers of refracting materials for the coating, designed such that the small reflections from all of the layers added together is very small, ensuring the highest-possible reflectivity from the metal surface.

Most mirrors (i.e. those made of metal) have a layer of free electrons; when a light wave approaches, a current is induced that causes radiation according to the law of reflection. The total amount of light which gets reflected can depend very strongly on the wavelength of the light, the incidence angle, or even the polarization of the light. Various reflection curves for simple metals can be found in the literature or on Wikipedia: . As you can see, depending on whether you are using blue light or red light, you might want aluminum, gold, or silver for your mirror.

David Schmid
 

(published on 03/06/2013)