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.
Focusing light with a magnifying glass can start a fire. 
( z1 possible :ARG1 ( z2 start :ARG0 ( z3 focus :ARG1 ( z4 light ) :instrument ( z5 magnifying-glass ) ) :ARG1 ( z6 fire ) ) )