Pupil

Real World Example

Imagine trying to read a book in a dimly lit room where you can barely see the words on the page. Just as you might adjust a lamp to let in more light, your pupil widens in low light conditions to allow more light to enter the eye. The pupil acts like the adjustable lamp in your eye, expanding or contracting to control the amount of light that reaches the retina, much like you would adjust the lamp's brightness to see clearly.