One of the most popular types of microscopes for kids and for use in laboratories is the light microscope, and if you’ve wondered how the lens of a light microscope might work, you may be surprised to learn that a light microscope functions a lot like a refracting telescope! (with some minor differences which are pointed out below).

In an earlier blog post we discussed that light microscopes have two lenses, an ocular and an objective lens. A light microscope works by gathering a focused, visible beam of light that passes through and around a specimen with the objective lens (the lens closest to the specimen). The beam of light hits the specimen from below, and the microscope’s objective lens focuses on the same point from above, bringing the specimen’s image into focus within the microscope’s tube. Finally, this image is magnified for the person using the microscope by a secondary lens (the ocular lens, sometimes called the eyepiece).

What kind of light sources does a light microscope use?

A light microscope can use several different types of light sources. Your microscope can either have an electric or battery powered light source at the base, which illuminates the specimen from below, or it can work using ambient light, reflected up around and through the specimen via a small mirror at the bottom of the microscope.

Light microscopes use a condenser – a lens system which focuses the light from the source on a small, illuminated point of the specimen. The objective lens of your microscope is focused on this same point (from above).

Light microscope lenses vs. refracting telescope lenses

There are several differences between a refracting telescope and light microscope. First, a telescope uses a large objective lens as a means to gather a large amount of light and bring a distant object (like a star) into focus. A light microscope, on the other hand, uses a small objective lens since it only needs to acquire a narrow, focused amount of light as it passes through a specimen.

Secondly, a refracting telescope uses a fixed objective lens and interchangeable eyepieces to adjust the level of magnification, but a light microscope is just the opposite. The eyepiece (or ocular lens) of a light microscope is fixed in place, and most light microscopes allow you to rotate between several objective lenses to adjust the level of magnification (pictured at the top of this article).

A telescope’s primary function is to gather light, whereas a light microscope’s lenses magnify a specimen and utilize light to allow users to examine specimens by use of the light.

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