Question

From left, a lens labeled 1 flat on the left and convex on the right, a thick lens labeled 2 double convex, a lens labeled 3 convex on the right and slightly concave on the left, a lens labeled 4 flat on the left and concave on the right, a lens labeled 5 concave on both left and right, a thin lens labeled 6 double convex.
Which lenses are convex? Check all that apply.

1
2
3
4
5
6

Answer 1

Convex lenses: 1, 2, 3, 6.

Brief reasons:
- 1: plano-convex (one flat, one convex) — converging.
- 2: double convex — converging.
- 3: meniscus with stronger convex side (convex on right, only slight concave on left) — overall converging.
- 6: thin double convex — converging.

Lenses 4 (plano-concave) and 5 (double concave) are concave/diverging.