2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

In response to increased light you pupil will shrink, in dim light your pupil will dilate (grow bigger). This happens because you iris will contract to make the pupil smaller or relax to make it bigger. Radial muscles also make the pupil bigger by contracting.
To focus at different distances the lens in your eye adapts its shape:
If an object is near, ciliary muscles will contract which relaxes the suspensory ligaments so that the lens is fat;
If an object is far, ciliary muscles will relax making the suspensory ligaments tight so they pull the lens thin.

Recomend a look at this page:
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/electrical/thenervoussystemrev4.shtml