Final answer:
The illusion that arises when the terrain around the runway is higher than the runway itself is called a visual illusion or a runway slope illusion. It can affect a pilot's perception of the runway's slope, potentially leading to an incorrect approach or landing.
Step-by-step explanation:
The illusion that arises when the terrain around the runway is higher than the runway itself is called a visual illusion or a runway slope illusion. This illusion occurs when the surrounding terrain creates a slope that visually affects the pilot's perception of the runway's slope. For example, if the ground slopes upward towards the runway, it can make the pilot perceive that the runway is tilted downwards, potentially leading to an incorrect approach or landing.