Final answer:
When a dog is walking toward you, the image on your retina becomes larger as the dog gets closer to you. This change in the size of the image on the retina helps you perceive the dog as getting closer.
Step-by-step explanation:
When a dog is walking toward you, the image on your retina becomes larger. This is because the dog is moving closer to you, which causes the light rays from the dog to converge onto a smaller area of your retina. This change in the size of the image on the retina is known as a change in the visual angle.
For example, if the dog is far away from you, the image on your retina will be relatively small. However, as the dog gets closer, the image on your retina will become larger because more light rays from the dog are entering your eye. This increase in the size of the image on the retina helps you perceive the dog as getting closer to you.