Cathy carefully walks down the aisle of the dark movie theatre. After hesitating a few times, she finds an empty seat. After a short while she can distinguish her friend Suzy sitting a few rows ahead of her. Cathy has experienced the phenomenon known as:

dark adaptation

Explanation:

Dark adaptation: The term dark adaptation refers to the phenomenon through which an individual's eyes can adjust to darkness after he or she has been exposed to light for a specific period. Eventually, the eyes adapt to the darkness by recovering it and becomes more sensitive in dim light. It happens after the pupils of a person gets dilated and changes or alters the cones and rods of the person's eyes.

In the question above, Cathy has experienced the phenomenon known as dark adaptation.