BRAINCAKELine Spectra
When the light from a hot gas is passed through a prism or diffraction grating, it forms a line spectrum: a set of sharp coloured lines at particular wavelengths on a dark background.
Electrons in an atom can only occupy discrete energy levels. When an excited electron drops from a higher level E1 to a lower level E2, the atom emits a single photon whose energy equals the difference between the levels, hf = E1 - E2.
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Key terms in this lesson
- Photon
- A discrete packet, or quantum, of electromagnetic energy.
- De-excitation
- The process by which an electron in an excited atom falls to a lower energy level, emitting a photon whose energy equals the difference between the two levels.
More in The Photoelectric Effect
- Excitation Using Photons
- De-excitation
- Fluorescence
- Fluorescent Tube
- Excitation of Hydrogen Atoms
- The Discovery of Helium
- The Dual Nature of Light
- De Broglie's Hypothesis
All 19 lessons in The Photoelectric Effect · All AQA AS-level Physics topics