A magnifying lens is a convex lens made of either glass or some other transparent material that is used to magnify and concentrate light. When used with sunlight it can be used to ignite tinder.
I carry a credit-card sized fresnel lens in my wallet. Why not?
Types Of Lens
Traditional convex lenses are available in both framed and unframed versions. These are effective, but heavy and fragile.
Fresnel lenses are thinner, lighter, and are often made of more durable materials such as plastic or acrylic.
Fresnel lenses are powerful and can concentrate the power of the sun.