Final answer:
Dark adaptation is the process by which the eyes adjust to low levels of light. It involves the dilation of the pupils and the activation of rod cells in the retina, allowing us to see more clearly in dim light.
Step-by-step explanation:
The process described in the question, where Peter gradually improves his ability to see things in a dimly lit theater over time, is known as dark adaptation.
Dark adaptation is the process by which the eyes adjust to low levels of light. It involves the dilation of the pupils and the activation of rod cells in the retina, which are responsible for seeing in low light conditions.
During dark adaptation, it takes about 10-20 minutes for our vision to fully adjust to darkness, allowing us to see more clearly in dim light.