← Modern Physics
3 Atomic spectra & energy levels
Electrons occupy discrete energy levels. A photon is emitted (or absorbed) when an electron drops (or jumps) between levels, with energy exactly equal to the gap. Transition energy ΔE = E<sub>high</sub> − E<sub>low</sub> = h f Gives a line spectrum: specific wavelengths only.Emission vs absorption
- Emission: electron drops a level → photon emitted → bright line.
- Absorption: photon absorbed → electron jumps up → dark line in a continuous spectrum.
- Line spectra are a “fingerprint” unique to each element.