Complex sentence: This is why spotlighting has become a popular way of locating members of a population; when a strong light is directed at the eyes of a glider, the observer will see two bright red orbs reflecting back.
Split into simpler sentences: This is why spotlighting has become a popular way of locating members of a population. When a strong light is directed at the eyes of a glider, the observer will see two bright red orbs reflecting back.