Convex and Concave Lenses

Front

Lens Noun

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[lenz]

Back

Lens

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A transparent optical device with one or more curved surfaces that refracts light to form an image.

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Example: This diagram shows a convex lens, identifying its principal axis, optical axis, focal point (F), and focal length (f).

Front

Refraction Noun

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[ri-frak-shun]

Back

Refraction

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The bending of a light ray as it passes from one transparent medium to another with a different optical density.

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Example: Parallel rays of light bend, or refract, as they pass through a convex (converging) lens, meeting at a single spot called the focal point.

Front

Convex Lens Noun

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[kon-veks lenz]

Back

Convex Lens

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A lens that is thicker at its center than at its edges, causing parallel light rays to converge to a point.

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Example: This diagram shows how a convex lens, which is thicker in the middle, bends parallel light rays inward to meet at a single focal point.

Front

Concave Lens Noun

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[kon-kayv lenz]

Back

Concave Lens

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A lens that is thinner at its center than at its edges, causing parallel light rays to diverge or spread out.

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Example: This diagram shows a concave lens, which is thinner in the middle. It causes parallel light rays to spread out (diverge) as if from a single focal point.

Front

Converging Lens Noun

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[kun-vurj-ing lenz]

Back

Converging Lens

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A lens, typically convex, that causes parallel light rays passing through it to come together at a focal point.

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Example: This diagram shows how a converging lens bends parallel light rays to meet at a single spot, called the focal point.

Front

Diverging Lens Noun

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[dy-vurj-ing lenz]

Back

Diverging Lens

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A lens, typically concave, that causes parallel light rays passing through it to spread out as if from a point.

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Example: A diverging lens spreads out parallel light rays, making them appear to originate from a single point called the virtual focal point (F).

Front

Focal Point Noun

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[foh-kul point]

Back

Focal Point

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The specific point at which light rays parallel to the principal axis converge after passing through a converging lens.

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Example: A converging (convex) lens bends parallel rays of light so they meet at a single spot called the real focal point.

Front

Focal Length Noun

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[foh-kul length]

Back

Focal Length

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The distance measured from the center of a lens to its focal point along the principal axis.

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Example: This diagram shows parallel light rays passing through a converging lens and bending to meet at the real focal point.

Front

Principal Axis Noun

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[prin-suh-pul ak-sis]

Back

Principal Axis

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An imaginary line passing perpendicularly through the optical center of a lens and its focal points.

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Example: This diagram shows the principal axis as the main horizontal line passing through the center of a convex lens and its focal points.

Front

Real Image Noun

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[reel im-ij]

Back

Real Image

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An image formed by the actual convergence of light rays, which can be projected onto a physical surface or screen.

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Example: This ray diagram shows light rays from an object reflecting off a concave mirror and converging at a single point to form an inverted real image.