Introduction

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Energy levels and photon emission provide some of the strongest evidence for the quantum nature of atoms. Electrons within atoms can only exist in specific energy levels, and when they move between these levels they absorb or emit energy in the form of photons. This explains why different elements produce unique line emission spectra and provides important evidence that energy is quantised.

In this topic, students learn how electrons become excited, how photons are emitted when electrons return to lower energy levels, and how to apply the relationship between photon energy and frequency. These ideas underpin many areas of modern Physics, including spectroscopy, quantum theory and atomic structure.

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AQA A Level Physics Specification: 3.2.2.3 Energy Levels and Photon Emission
 

What You Need to Know

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• Understand that electrons occupy discrete (quantised) energy levels within atoms.

• Explain how electrons become excited by absorbing energy.

• Describe how excited electrons return to lower energy levels by emitting photons.

• Understand that the energy of an emitted photon is equal to the difference between two energy levels.

• Apply the equation E = hf to calculate the energy of a photon.

• Explain why each element produces a unique line emission spectrum.

• Describe how line emission spectra provide evidence for quantised energy levels.

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Downloadable Topic Pack

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Energy Levels and Photon Emission Past Exam Question & Answer Pack

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Related Topics
 

• The Photoelectric Effect

• Wave–Particle Duality

• Electromagnetic Radiation

• Atomic Structure and Specific Charge

• Collisions of Electrons with Atoms