Question

what are convex lenses?
which lens in the image is a convex lens?
lens a
neither lens is a convex lens
lens b
a convex lens is thicker at the center and converges light, focusing it to a point.
in contrast, a concave lens is thinner at the center and causes light to diverge.
convex lenses bring light together, while concave lenses spread it apart

Explanation:

A convex lens is thicker at the center. Lens B is thicker at the center, while Lens A is thinner at the center (a concave lens).

Answer:

Lens B