Why does the eye-lens not have to do all the work of converging incoming light rays?

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

An object is moved closer to an eye. What changes must take place in the eye in order to keep the image in Sharp focus?

Explain why, when it is getting dark at night, it is impossible to make out the color of cars on the road.

Nocturnal animals (animals which sleep during the day and come out at night) tend to have wide pupils and lot of rods in their retinas. Suggest reasons for this.