Page 12 Microscopes
One square centimeter of your skin’s surface contains more than 100,000 cells. But no matter how closely you look with your eyes alone, you won’t be able to see individual skin cells. That is because, like most cells, those of your skin are very small. Until the late 1600s, no one knew cells existed because there was no way to see them. The cell theory could not have been developed without microscopes.
The first property, magnification, is the ability to make things look larger than they are. The lenses in light microscopes magnify an object by bending the light that passes through them. Since a compound microscope uses more than one lens, it can magnify an object more than one lens by itself. The first lens, near the specimen, magnifies the object. Then a second lens, near the eye, further magnifies the enlarged image. The total magnification of the microscope is equal to the magnifications of the two lenses multiplied together. For example, suppose the first lens makes an object look 10 times bigger than it actually is, and the second lens makes the object look 40 times bigger than it actually is. The total magnification of the microscope is 10 × 40, or 400.