...a Reflector

Silver has a special relationship with light and has the highest reflectivity of all metals. Applications as a reflective coating is one of the industrial uses that contributes to silvers intrinsic material values.

According to the Silver Institute:

Silver’s unique optical reflectivity, and its property of being virtually 100% reflective after polishing, allows it to be used both in mirrors and in coatings for glass, cellophane or metals.

Everyone is accustomed to silvered mirrors. What is new is invisible silver, a transparent coating of silver on double pane thermal windows. This coating not only rejects the hot summer sun, but also reflects inward internal house heat. A new double layer of silver on glass marketed as "low E squared" is sweeping the window market as it reflects away almost 95% of the hot rays of the sun, creating a new level of household energy savings. Over 250 million square feet of silver- coated glass is used for domestic windows in the U.S. yearly and much more for silver coated polyester sheet for retrofitting windows.

One out of every seven pairs of prescription eyeglasses sold in the U.S. incorporates silver. Silver halide crystals, melted into glass can change the light transmission from 96% to 22% in less than 60 seconds and block at least 97% of the sun's ultraviolet rays. The change is endlessly reversible.