Which parts of the eye cause rays of light to converge on the retina ?

What shape are your eye-lenses:

(a) when you look at your hand ?

(b) when you look at a distant tree ?

suggest how your irises help to protect' the retinas of your eyes from damage by bright light.

Which part causes the greatest convergence ?

Which part brings the image into sharp focus on the retina? How does it do this?