The Ammonia Maser: Feynman's Physics Explained
The ammonia molecule is a perfect real-world two-state system: its nitrogen atom can sit on either side of the plane of three hydrogen atoms, and quantum tunneling lets it flip between them. This possibility splits the ground state into two very close energy levels. The ammonia maser uses a beam of molecules prepared in the upper state to amplify microwaves at exactly the frequency of that tiny energy gap — an ancestor of the laser.
The big idea
A molecule flipping between two states can amplify microwaves.
Think about it
How can a particle 'tunnel' from one side of a barrier to the other without ever having enough energy to climb over it?
← More Physics (Feynman Lectures) guides · Explore the Physics (Feynman Lectures) module →
📧 Get a free brain-teaser every morning
Join thousands of families learning something new each day.
Subscribe free