The two important points to notice are these: First, the magnifying glass is too close to the eye for the light to be brought to a focus before it reaches the eye; the light is bent toward a focus, but it reaches the eye before the focus is formed. The focus is formed for the first time on the retina itself. Second, the magnifying glass bends the light on its way to your eye so that the light crosses sooner in your eye and spreads out farther before it comes to a focus. This forms the larger image, as you see in the simple diagram, Figure 82.
Fig. 85. This is the way a concave mirror forms a magnified image.
Fig. 86. The concave mirror forms an image of the burning candle.
How the microscope works. But the microscope is different. It works like this: The first lens is put very near the object which you are examining. This lens brings the light from the object to a focus and forms an image, much larger than the object itself, high up in the tube. If you held a piece of paper there you would see the image. But since there is nothing there to stop the light, it goes on up the tube, spreading as it goes. Then there is another lens which catches this light and bends it inward on its way to your eye, just as any magnifying glass does. Next the lens in the eye forms an image on the retina. The diagram (Fig. 84) will make this clearer. (A real microscope is not so simple, of course, and usually has two lenses wherever the diagram shows one.) What actually happens is that the first lens makes an image many times as big as the object; then you look at this image through a magnifying glass, so that the object is made to look very much larger than it really is. That is why you can see blood corpuscles and germs and cells through a microscope, when you cannot see them at all with your naked eye.
