# A-level Physics (Advancing Physics)/Energy Levels/Worked Solutions

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**The following table gives the wavelengths of light given off when electrons change between the energy levels in hydrogen as described in the first row:**

Transition of n | 3→2 | 4→2 | 5→2 | 6→2 | 7→2 | 8→2 | 9→2 | ∞→2 |
---|---|---|---|---|---|---|---|---|

Wavelength (nm) | 656.3 | 486.1 | 434.1 | 410.2 | 397.0 | 388.9 | 383.5 | 364.6 |

Colour | Red | Blue-green | Violet | Violet | (Ultraviolet) | (Ultraviolet) | (Ultraviolet) | (Ultraviolet) |

**1. Calculate the potential energy of an electron at level n=2.**

**2. Calculate the difference in potential energy between levels n=2 and n=3.**

This time, let's derive a general formula:

**3. What is the potential energy of an electron at level n=3?**

**4. If an electron were to jump from n=7 to n=5, what would the wavelength of the photon given off be?**