Atoms and Light

Absorption and emission

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Atoms have discrete energy levels.
• Photons are absorbed or emitted when atoms jump between levels.
• Ordinary light comes from random spontaneous emission.

Steps

1. Energy levels
2. A red laser
3. Photons per second
4. A green photon
5. Can heat do it?
6. Why X-ray lasers are hard