Image Formed Microscopes

Images Formed by Simple and Compound Microscopes

A simple microscope or magnifier is a lens or a combination of lenses to use with the eye. But one image is formed and that is upon the retina. The enlarged image has all its parts in the same position as they are in the object itself, that is, the image appears exactly as with the naked eye, except that it is larger (DIAGRAM).

A compound microscope is one in which a lens, or combination of lenses, called an objective, forms a real image, and this real image is looked at, by the eye and a magnifier, or ocular. The image seen has the object and its parts inverted. In the compound microscope then, two images are formed, one by the objective independent of the eye, and the other on the retina by the action of the eye lens of the ocular and the cornea and crystalline lens of the eye.

Real Images

A real image is one formed by a lens or other optical instrument, like a concave mirror. It is called real because, entirely independent of the eye, it forms a picture of an object. This is the kind of image which makes photography possible, also the magic lantern, and moving pictures on a screen.

Virtual images

In all diagrammatic drawings showing the microscope when looking directly into it, an enlarged, imaginary object is shown out in space. This is frequently called a virtual image. In the projection microscope there is an actual or real, enlarged image on a screen which the observer looks at as if it were a large object. If one keeps in mind that virtual images are purely imaginary, and that real images are produced by actual rays of light, it will help to avoid confusion and wrong interpretations.

In every case where an object is seen, light rays must pass from the object to the eye, and these rays entering the eye must form an image on the retina. It is the retinal image which furnishes the brain the stimulus for vision.

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