Magnifying Glasses and Microscopes

Telescopes allow you to see distant objects, making them appear closer and larger than they really are. Microscopes also make objects appear nearer and larger, but these objects are very close and small. Here's the basic recipe for a microscope: Use a very-short-focal-length lens as the objective. Place object just outside its focal point. This creates a real image, far larger than the object. Now, use an eyepiece as a magnifying glass to make the magnified image appear even larger.

Activities & Practice
to do as you read

1. Watch this video explanation.

Microscopes and Refracting Telescopes compared How are microscopes and telescopes similar, and how are they different?

SAME Both use an objective lens to create a real image.

DIFFERENT The objective lens of a telescope has a long focal length (typically meters long), and the object being examined is of course very far away. Therefore d_i << d_o and the magnification is far less than one. Close to zero, in fact. (Imagine you are looking at Jupiter; the real image of Jupiter produced by the objective lens is very much smaller than Jupiter itself. Conversely, the objective lens of a microscope has a very short focal length (typically around a millimeter.) The objective lens is brought very close to the thing being examined — an amoeba, perhaps. This makes d_i >> d_o and the magnification is far greater than one; the image of the amoeba is much bigger than the amoeba itself.