A magnifying glass (called a hand lens in laboratory contexts) is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle (see image). A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to create a hot spot at the focus for fire starting.
You can start a campfire with a magnifying glass.
( z1 possible :ARG1 ( z2 start :ARG0 ( z3 you ) :ARG1 ( z4 fire :location ( z5 camp ) ) :instrument ( z6 magnifying-glass ) ) )