The convex lens

Convex lenses converge light to a focus. Image is real or virtual. Power is positive.

What is it like to look through?
1. Close to object - it magnifies.
2. Far from eye - image upside down.

Uses of convex lenses
Eye camera overhead projector focus sunlight projector
microscope simple telescope glasses (correct for long sight) magnifying glass

The concave lens

Concave lenses diverge or spread out the light. There is no real focus. Image is always virtual. Power is negative.

What is it like to look through?
The image that you see is always the right way up and smaller.

Uses of concave lenses
glasses (correct for short sight) spy holes in doors
some telescopes back window of coaches