Brenda is standing on the beach; the sea is choppy. she observes that the crests of distant waves appear not only smaller, but also closer together than do the crests of waves nearer the beach. this example illustrates a depth cue known as:

this example illustrates a depth cue known as: Linear perspective

Linear perspective refers to the perception of size, position, and shape of an object based on the subject's perspective.

Many factors could influence one's linear perspective such as elevation, distance between the subject and the object, etc.