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. 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. A sheet magnifier consists of many very narrow concentric ring-shaped lenses, such that the combination acts as a single lens but is much thinner. This arrangement is known as a Fresnel lens.
The magnifying glass is an icon of detective fiction, particularly that of Sherlock Holmes as well as the symbol for Searching.
Sherlock, named after fictional detective Sherlock Holmes, was a file and web search tool created by Apple Inc. For the PowerPC-based "classic" Mac OS, introduced with Mac OS 8 as an extension of the Mac OS Finder's file searching capabilities. Like its predecessor (System 7.5’s totally revamped 'Find File' app, adapted by Bill Monk from his 'Find Pro' shareware find program), Sherlock searched for local files and file contents, using the same basic indexing code and search logic found in AppleSearch. Sherlock extended the system by enabling the user to search for items through the World Wide Web through a set of plugins which employed existing web search engines. These plugins were written as plain text files, so that it was a simple task for a user to write a Sherlock plugin.
Sherlock was replaced by Spotlight and Dashboard in Mac OS X 10.4 Tiger, although Apple continued to include it with the default installation. Since most of the standard plug-ins for Sherlock provided by Apple itself no longer function, it was officially retired and removed in the release of Mac OS X 10.5 Leopard in 2007.