Which one of the following statements about the aperture of a convex lens is correct?

The aperture of a convex lens is defined as the effective diameter of its circular outline or the light-gathering area [3]. While the focal length and radius of curvature are intrinsic geometric and optical properties determined by the lens's material and surface curvature, the aperture is a physical dimension representing the size of the lens opening [3]. Unlike spherical mirrors where the radius of curvature is twice the focal length (R=2f) for small apertures [2], this specific relationship does not strictly hold for lenses as their focal length also depends on the refractive index. Crucially, the aperture is an independent physical parameter; cutting a lens or reducing its aperture changes the intensity of the image due to less light passing through, but it does not alter the focal length or the radius of curvature of the lens surfaces.

Sources

1. [2] https://www.khanacademy.org/science/ap-physics-2/x0e2f5a2c:geometric-optics/x0e2f5a2c:reflection-and-mirrors/v/spherical-mirrors-radius-of-curvature-focal-length
2. [3] https://www.ncbi.nlm.nih.gov/books/NBK587441/