Concave Lens: Definition & Uses

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  • 0:05 What is a Concave Lens?
  • 1:03 Uses of Concave Lenses
  • 2:58 Lesson Summary
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Lesson Transcript
Instructor: Josh Corbat

Josh has taught Earth Science and Physical Science at the High School level and holds a Master of Education degree from UNC-Chapel Hill.

Convex lenses get all the glory. They are used for magnification, in cameras, and in countless other devices. Concave lenses, on the other hand, are often underappreciated. In this lesson, discover what concave lenses are and what they are used for.

What is a Concave Lens?

Lenses are incredibly important to us. In fact, it can be said that lenses have changed our lives as human beings. Without lenses, we would have to rely on our natural eyesight (which would be unfortunate for those of us without 20/20 vision), we wouldn't have any type of photography, and we wouldn't have television or movies. Do I even need to continue this list to prove the point that lenses have made our lives very different?

There are two main types of lenses: convex and concave. Convex lenses often get all the credit. They are the type of lens responsible for magnification and are the most common lens used in photography and other common applications. Concave lenses, though, serve an important role as well. A concave lens is any lens that has an inward curve in the middle. In other words, the edges of the lens are thicker than the middle. This causes light that enters the lens to spread out, or diverge. In effect, this makes images appear smaller when viewed through a concave lens.

Light being passed through a concave lens. As you can see, the light is spreading out, or diverging, as it passes through the lens.
Concave lens

Uses of Concave Lenses

Although not as common as convex lenses, concave lenses have several uses. Concave lenses are used to treat a condition called nearsightedness (also called myopia). Concave lenses spread out light before it hits the part of the eye that senses light, causing images to appear much more clearly for people with this condition.

Flashlights are much more useful if the beam of light is bigger. Imagine trying to find something in a dark room using only a beam of light an inch or two wide! Concave lenses are used in flashlights to spread out the beam of light so that it covers a much wider area. Depending on the brightness of the light bulb, the beam can sometimes be spread out over quite a large area.

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