Pupil reflex – change of pupil size in response to changing light
Pupil reflex is the reduction or increase in the size of the pupil in response to increased or reduced light intensity.
The school pupil’s reflection (pupil reflex) in the mirrors changed in size.
The iris in our eye adjusts the size of the pupil in response to the level of light. It opens the pupil wider in dim conditions, and reduces the opening when it gets brighter. This is a reflex action – a function performed by the nervous system and effectors (in this case the antagonistic muscles of the iris) without any thought.
Imagine waking up in a dark bedroom. Your pupil would be large (dilated) to let in as much light as possible to see in the gloom. Then imagine opening the curtains to reveal a sunlit snowscape – so bright that your pupil would immediately constrict, or go smaller. This is pupil reflex.