What is the source of the energy that causes electrons to be emitted from the surface?

Mike and mitchell decide to have a foot race. they mark off a stretch of 100 yards, and recruit cindy to work the stopwatch. after running the race and looking at the results, cindy declared that mitchell was the fastest. so how did the boys times compare?

Asolid that forms and separates from a liquid mixture is called

What can be found in the ionosphere