When you enter from bright light to dark room what happens and why?

When you enter a dark room from bright light, your eyes experience a sudden change in illumination. The pupils dilate to allow more light to enter, which helps improve your vision in low-light conditions. However, it takes time for the photoreceptor cells in your eyes, particularly the rods, to adjust and become more sensitive to the darkness. This process, known as dark adaptation, can take several minutes for optimal vision in low light.