Key relationship
Eγ=13.606(1/nf²−1/ni²) eV; λ=hc/|Eγ|.
Physics · Class 12
Hydrogen spectral transitions
A spectral line records the energy difference between levels, not the energy of either level alone. Downward transitions emit photons; upward transitions absorb matching photons. A set ending at n2 forms the Balmer series.
Open the interactive experiment →Hydrogen spectral transitions
நிறமாலை வரி இரு நிலைகளின் ஆற்றல் வேறுபாட்டைக் காட்டும். கீழ்நோக்கிய மாற்றம் ஃபோட்டானை வெளியிடும்.
Key notes, relationships and model limits
Remember
A spectral line records the energy difference between levels, not the energy of either level alone. Downward transitions emit photons; upward transitions absorb matching photons. A set ending at n2 forms the Balmer series.
Common trap
No photon is produced by merely selecting the same level twice.
Model limits
Hydrogen without fine structure; positive signed Eγ indicates emission. Equal levels have no photon and no wavelength, represented by an explicit no-transition state.
What you will learn
Calculate lines and distinguish emission from absorption.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
3→2 gives about1.890 eV and656.1 nm in this ideal model.
Why this matters
The model connects hydrogen spectral transitions with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
The hydrogen3→2 transition is?
- Absorption
- Emission
- No energy change
Read the explanation
The final energy is more negative, releasing a positive photon energy.
Course connection: Class XII Chapter 12. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.