Convex Lens
Definition
A lens thicker in the middle that converges light rays — the magnifying glass lens.
Symbol: · Unit: m (focal length)
Technical definition
A converging lens (biconvex typical) with positive focal length. Parallel rays refract through the far focal point. Forms real inverted images of distant objects; virtual magnified images when the object is within the focal length. The lensmaker's equation relates f to curvatures and refractive index.
Example
A magnifying glass is a convex lens: hold it close to text (inside f) for an enlarged virtual image; project sunlight with it and paper burns at the real focus.
Convex lenses do not only magnify — with distant objects they make smaller real images (that is how camera lenses work). Whether the image is magnified or diminished depends on object distance, not just lens type.