Title: Light-emitting diode.
Question: How can light emission be varied from violet to amber?

Title: Russian Soviet Federative Socialist Republic.
Question: How long did the new Russian Soviet state go unrecognized by other countries?

Title: Protestantism.
Question: What type of missionaries were taught in Geneva?

Title: John von Neumann.
Question:
In what year did Von Neumann's mother and siblings join him in U.S?