Bad Qubits — Learn Quantum by Doing

Multiple choice

Why does excited hydrogen gas produce a discrete set of sharp spectral lines rather than a continuous rainbow?

An atom can only emit or absorb a photon whose energy matches the difference between two allowed (quantized) internal energy levels
The electron radiates continuously while spiraling inward, producing a few preferred colors
Only photons traveling at exactly the speed of light survive, and these happen to be discrete colors
Hydrogen atoms emit all wavelengths equally, but a prism only transmits a few of them