A magnifier, usually composed of a lens and a mirror handle
The reason why magnifiers are able to zoom in objects lies in the curved surfaces of lenses. According to the law of refraction, magnifiers make the image on retinas vary proportionately to the visual angles formed between the object and eyes, the bigger the visual angle, the clearer of the object. It means that, on the contrary to our normal thinking mode, more details can be observed when the object is further to the magnifier.
What's more, magnifiers are widely applied in our daily lives. For example, when elders read, for their deterioration of eyesight, they often take a magnifier so as to see clearly words on books or newspapers. The film projector, with the application of a magnifier, shows pictures on screen big enough for people far away to make out. The camera lens are also made from magnifiers, for which reason, we can get whatever size of photos as we expect, by adjusting the distance between lens and films. Even glasses belong to one kind of magnifier.
Moreover, besides the main function of the magnifier to enlarge objects, magnifiers can also focus the sun's rays or highlight on the paper to make fire, and the more intense the light, the easier to get fired.