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Types of Reflecting Lens

Reflecting lenses differ from refracting lenses in that they do not allow light rays to pass through the lens. A silvering compound is applied to one side of a lens to create this effect. Depending on what type of reflecting lens is present --- convex, concave or plane --- determines what the effect is on the light rays after they have encountered the lens. Reflecting lenses are also commonly referred to as "mirrors."

Opacity
- The opacity of a reflecting lens can vary from completely opaque to transparent. Transparent, two-way and pyrolytic reflective surfaces lack the silvered side of an opaque mirror but are better able to withstand moisture. Completely opaque mirrors are called "clear mirrors."
Materials
- Glass, plastic, and metal can all be made into reflecting lenses. Metal is used where safety is the primary concern. Plastic allows for an economy in production that will create an affordable end product. Glass is used where the highest quality of reflecting lens is needed, such as for microscopes, telescopes and other applications where the image quality is the primary concern.
Convex
- Convex mirrors are shaped like an upside down bowl. Light rays diverge or move away from each other when they strike the surface. This spreads the reflection over a broader surface of the lens, as if the focal point was located behind the lens.
Concave
- Concave reflecting lenses have an inward curve to their shape. Light rays that hit the surface are reflected in a diagonal direction --- both upward and downward --- that cross, or converge to create a concentrated focal point in front of the lens.
Plane
- Plane mirrors are completely flat; the light rays bounce off them in the exact order in which they arrived. These mirrors are useful in situations where a real image, one with little distortion, is required.

Astronomy