How Does Magnification Work?
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Light
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Magnification starts with light. Without light, you would not be able to see any image, magnified or not. Light travels at a speed of 186,000 miles per second. This speed is the average for light traveling through air. Light will travel through other substances at different speeds. When rays of light hit the material of a lens, the speed of the light changes as it goes through the lens. The change in speed makes the light ray bend, or change direction.
The Retina
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Your eye contains a retina, which is like a light-sensitive screen. The retina, along with other parts of the eye (e.g., the optic nerve) allows you to see images around you. The size of an image is affected by how much space the image takes up on the retina. The more space the image takes up, the larger it appears to the viewer. The smaller the space the image takes up, the smaller it appears to the viewer.
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Lenses
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A convex lens bends the light that goes through it toward a focal point. The light spreads out again past this focal point. Magnifying glasses are convex lenses. When you use one, the lens bends the light rays so that they come together and focus on the lens within your eye. The light then spreads out as the rays continue past the focal point, and they hit the retina of the eye. The spreading of the light makes the image viewed appear much larger than it really is because it causes the image to take up more space on the retina. Moving the magnifying glass closer or farther away from the eye will change how much the light is spread on the retina. The closer the magnifying glass is to the eye, the bigger the image will appear.
Multiple and Natural Magnifiers
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Although magnification is possible with only one lens, it also can be achieved by using more than one. Series of lenses, for instance, are sometimes used in telescopes to continue to bend light rays until an eyepiece lens finally can bring the focal point to our eye. Some microscopes also use series of lenses to increase the magnification possible. Additionally, sometimes magnification occurs in nature because of natural lens formation. A water droplet, for example, can act like a convex lens and can bend light such that whatever is underneath the water droplet appears bigger to us.
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