Magnifying Glass
Sunlight focused by a converging magnifying glass can burn paper. Light rays from the sun are nearly parallel and cross at the focal point of the lens. The more powerful the lens, the closer to the lens the rays will cross.
Source
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"OpenStax College, College Physics. January 1, 2013."
http://cnx.org/content/m42470/latest/?collection=col11406/1.7
OpenStax CNX
CC BY 3.0.