1. Light effects which color flower a hummingbird will visit for nectar.
2. Light helps me avoid walking into walls by illuminating them.
3. Light aids circling hawks discover small prey for lunch.
4. Light illuminates the highway so while driving we can avoid obstacles at night.
5. Light causes sunflowers to follow the sun daily.
6. When an anti-submarine helicopter hovering fifty feet above the ocean surface with its sonar unit dipped to a search depth experiences a double engine failure and falls into the sea, the surviving aviators, while bobbing around in their inflatable liferaft can use their survival signal mirrors to shine sunlight into a eyes of the pilot of a distant search aircraft and thereby get rescued.
Sorry, can't think of any more.