which part of eye controls the amount of light entering our eye? Iris or Pupil

The iris regulates the amount of light entering the eye by adjusting the size of the pupil in the following way:

 

(i) If the intensity of the light is low, the iris makes the pupil to expand to allow more light to enter the eye.

(ii) If the intensity of light is high, the iris makes the pupil to contract in order to decrease the amount of light entering the eye.