University of Edinburgh

BSL Physics Glossary - eyepiece lens - definition

In a telescope the lens near the eye is called the eyepiece lens. The other lens is larger and it is called the objective lens. The focal length of the eyepiece lens is short, because this is a fairly thick lens. For the thinner objective lens at the far end of the telescope, the focal length is longer. Why do we have 2 different lenses? The larger lens at the far end helps to collect the light into the telescope. The eyepiece lens provides the magnification to allow you to see the image.