Draw a diagram showing a normal iris and what happens to the iris when a light in shined into the human eye. (1 mark). What causes this to happen? (2 marks)

(Any diagram showing an iris that has constricted) 1 mark
In high light levels (1 mark) Accept reflex action due to increased photoreceptor action or words to that effect
circular muscles relax and radial muscles contract to constrict the iris (1 mark)