Modern Physics

Lyman α line

Ultraviolet Lyman series — transition to the ground state.

Lyman α line — interactive Modern Physics simulation. Ultraviolet Lyman series — transition to the ground state. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.

Lyman series

Ultraviolet Lyman series — transition to the ground state.

Transitions to n = 1 produce ultraviolet Lyman series lines at shorter wavelength than Balmer. Lyman-α at 121.6 nm is prominent in astrophysical hydrogen clouds and was key to probing the intergalactic medium.

• UV transition
• n → 1

Investigation brief

Plan the question before you open the lab

The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.

Driving question

Electrons dropping all the way down to the ground state (n = 1) emit the Lyman series. Compared to the Balmer series (dropping to n = 2), would you expect Lyman photons to have more or less energy?

Predictions to weigh

• Less energy than Balmer transitions.
• More energy (shorter wavelength) — dropping to the ground state releases a bigger energy gap than dropping to n = 2.
• The same energy as equivalent Balmer transitions.

Variable roles

What you set:

• Starting level n_i

What you measure:

• Emitted wavelength λ (nm)

How the investigation runs

1. Open the lyman-alpha preset and press Reset. This preset's default transition is n = 2 → n = 1 (Lyman-alpha).
2. Enable the emitted-wavelength readout.
3. Set the starting energy level n_initial for each trial (dropping down to n_final = 1) and record the emitted wavelength.

Governing equation

Lyman Series (Ground-State Transitions) — λ = hc/ΔE

Transitions ending at n_f = 1 release the largest possible energy gaps in hydrogen, since the ground state sits far below every excited level — producing the shortest-wavelength (highest-energy) spectral series, entirely in the ultraviolet.

What the printable worksheet asks students to work out

• For one trial, compute 1/λ = R(1/n_f² − 1/n_i²) using n_f = 1. Compare to the table. Confirm all three wavelengths fall below 122 nm — deep ultraviolet, invisible to the eye.
• Compare your Lyman wavelengths to the balmer-alpha experiment's visible-light wavelengths. Explain why dropping to n = 1 (a much bigger energy gap than dropping to n = 2) always produces higher-energy, shorter-wavelength photons.

Where this shows up beyond the lab

• Lyman-series ultraviolet light is almost entirely absorbed by Earth's atmosphere before reaching the ground. Explain why space telescopes (rather than ground-based ones) are needed to observe hydrogen's Lyman-alpha emission from distant astronomical objects.
• As n_i → ∞, 1/λ approaches R exactly (the series limit), corresponding to an electron barely escaping the atom entirely (ionization) rather than a specific transition. Using your formula, explain why the series limit represents the ionization energy from the ground state.

• AP Physics 2 — Unit 15: Modern Physics
• IB Physics — E.1 Structure of the atom
• General High School Physics — Modern physics intro
• NGSS High School Physics — Wave-particle duality of light

1. Welcome to Lyman Alpha
2. Select the atom
3. Press Play
4. Ultraviolet transition
5. Open the Properties panel
6. You did it!

Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.

Open Interactive Lab →

Download lab sheet →

The Bohr Model & Hydrogen Spectra