Most teachers are aware of the concept called wait time. Quoting from http://www.atozteacherstuff.com/pages/1884.shtml:
The concept of "wait-time" as an instructional variable was invented by Mary Budd Rowe (1972). The "wait-time" periods she found–periods of silence that followed teacher questions and students' completed responses–rarely lasted more than 1.5 seconds in typical classrooms. She discovered, however, that when these periods of silence lasted at least 3 seconds, many positive things happened to students' and teachers' behaviors and attitudes…