Source: https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-5-energy-levels-and-photon-emission

[Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [International A Level](https://senecalearning.com/en-gb/revision-notes/international-a-level.md) › [Physics](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics.md) › [Cambridge International](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international.md) › Energy Levels & Photon Emission

# Energy Levels & Photon Emission

Physics: Cambridge International A Level, topic 14.1.5

## Energy Levels in Atoms

Electrons in atoms must occupy a discrete energy level.

### Energy levels

![Energy levels](https://image-v2.cdn.app.senecalearning.com/courseImages/chemistry/1.1.2%20-%20Model%20of%20the%20atom/1.1.7.2%20-%20The%20electronic%20structure%20of%20calcium%20(s)-min.jpg)

- Electrons do not float around randomly in atoms.
- They can only be found at set energy levels.
- Each energy level is given a 'quantum number'.
- The ground state is the lowest energy level. The ground state has n = 1.
- The higher the energy level, the larger its quantum number, n.

### Transitions between energy levels

![Transitions between energy levels](https://image-v2.cdn.app.senecalearning.com/courseImages/physics/OCR%20Gateway/current.jpg)

- An electron can transition between energy levels by absorbing or emitting a photon of a specific frequency.
- If an electron emits a photon, it will drop in energy level.
- If an electron absorbs a photon, it will rise to a higher level.
 - In both cases, the photon must have energy exactly equal to the energy difference between the levels.

### Equation

![Equation](https://image-v2.cdn.app.senecalearning.com/courseImages/chemistry/1.1.2%20-%20Model%20of%20the%20atom/atom-1674878_640-min%20-%20Edited.jpg)

- The movement of electrons between energy levels can be represented in the equation:
 - $$\Delta E = E_1 - E_2 = hf = \frac{hc}{\lambda}$$
- This shows that the energy difference between levels one and two is equal to the energy of the emitted (or absorbed) photon.

### Excitation and ionisation

![Excitation and ionisation](https://image-v2.cdn.app.senecalearning.com/2018-08/63cb0f9c-ec7c-4cf9-86bb-16a05a220e87/Excitation.png)

- If an electron absorbs a photon and jumps up an energy level, we say it has been excited.
- If an electron absorbs a photon that is so energetic it is knocked out of the atom altogether, the electron has been ionised.

## Absorption Spectra

Electrons in atoms can only move between discrete energy levels. So an atom can only absorb or emit photons with particular frequencies (or wavelengths).

### White light - continuous spectrum

![White light - continuous spectrum](https://image-v2.cdn.app.senecalearning.com/2018-04/eb293c7a-ab94-42a6-9acb-4408d412e30b/shutterstock_122147881.jpg)

- White light contains all the colours in the visible part of the spectrum.
- When white light is passed through a prism or a diffraction grating, the colours are split up to produce a continuous spectrum.
- Continuous means there aren't any gaps or black lines.

### Cool gas - absorption spectra

![Cool gas - absorption spectra](https://image-v2.cdn.app.senecalearning.com/2018-08/d2a23054-6ddb-494a-86c2-5927d15dd9e1/Absorption%20spectra.png)

- A cool gas means a gas containing atoms in their ground state.
- When white light is passed through a cool gas, electrons in the ground state of the atom absorb certain frequencies of light and become excited.
- Most frequencies of the white light are not absorbed because they do not correspond to the difference between two energy levels in the atom.

### Absorption spectra 2

![Absorption spectra 2](https://image-v2.cdn.app.senecalearning.com/2018-08/abc0dd6f-d31d-4442-9dc0-7658901f4c64/Absorption%20spectra.png)

- If the light coming out of the cool gas is split by a prism (or diffraction grating), we see a continuous spectrum with black lines.
 - These lines are called absorption lines.
 - They are unique to each type of atom.

## Emission Spectra

Electrons in atoms can only move between discrete energy levels. So an atom can only absorb or emit photons with particular frequencies (or wavelengths).

### Excited gas

![Excited gas](https://image-v2.cdn.app.senecalearning.com/2018-08/de57a36a-c449-4ba7-b287-647c333c56fc/gas-smoke-cloud-.jpg)

- An excited gas contains atoms in excited energy states.
- These excited atoms contain electrons in high energy levels.
- As these electrons de-excite and fall back to lower energy levels, photons are emitted.

### Photon emission

![Photon emission](https://image-v2.cdn.app.senecalearning.com/2018-09/2d8dc5f4-adea-49bf-bbe7-4636c21df6da/light-diffraction-maxima-.jpg)

- These photons carry away energy from the atoms.
- The amount of energy (and so what frequency) the photons have depends on the difference in energy levels in the atom.
 - For every possible electron transition, there will be a unique frequency photon emitted.
- We see a series of bright lines when we pass the emitted light through a prism or diffraction grating.

### Emission vs absorption

![Emission vs absorption](https://image-v2.cdn.app.senecalearning.com/2018-10/6e5963a8-37fe-4503-8f88-f423651387fb/emission-vs-absorption-spectra.png)

- Compare the emission and absorption spectra produced by this gas.  
- We can see that the emission lines exactly match the frequencies of the absorption lines.
- This is because the lines correspond to the same energy differences in the atoms. The same energy photons are either emitted or absorbed.

## Test yourself on Energy Levels & Photon Emission

- What is the quantum number for the ground state of an electron?
- What is the correct equation for the change in energy between energy levels?
- When white light passes through a cool gas what happens?
- Which of these statements about absorption spectra are true?
- When an electron falls to a lower energy level what happens?

[Practise this topic for free](https://app.senecalearning.com/classroom/course/1b5bc325-d783-4d2c-99cd-5a7d913debfc/section/dbcedf02-aa3c-4b2d-876d-d79a49972cbd/session)

- Previous topic: [14.1.4 Collisions of Electrons with Atoms](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-4-collisions-of-electrons-with-atoms.md)
- Next topic: [14.1.6 Wave-Particle Duality](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-6-wave-particle-duality.md)

## Physics: Cambridge International A Level contents

### 1 Physical Quantities & Units
- 1.1 Physical Quantities & Units
  - [1.1.1 Use of SI Units](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-1-1-use-of-si-units.md)
  - [1.1.2 SI Prefixes, Standard Form & Converting Units](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-1-2-si-prefixes-standard-form-and-converting-units.md)
  - [1.1.3 End of Topic Test - Units & Prefixes](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-1-3-end-of-topic-test-units-and-prefixes.md)
  - [1.1.4 Avogadro's Constant](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-1-4-avogadros-constant.md)
  - [1.1.5 Scalars & Vectors](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-1-5-scalars-and-vectors.md)
- 1.2 Errors & Uncertainty
  - [1.2.1 Measuring Length, Time & Volume](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-1-measuring-length-time-and-volume.md)
  - [1.2.2 Measuring Temperature](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-2-measuring-temperature.md)
  - [1.2.3 Circuit Measurements](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-3-circuit-measurements.md)
  - [1.2.4 Limitation of Physical Measurements](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-4-limitation-of-physical-measurements.md)
  - [1.2.5 Uncertainty](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-5-uncertainty.md)
  - [1.2.6 Estimation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-6-estimation.md)
  - [1.2.7 Displaying Data](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-7-displaying-data.md)
  - [1.2.8 End of Topic Test - Measurements & Errors](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/1-2-8-end-of-topic-test-measurements-and-errors.md)

### 2 Kinematics
- 2.1 Equations of Motion
  - [2.1.1 Motion in a Straight Line](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/2-1-1-motion-in-a-straight-line.md)
  - [2.1.2 Graphs of Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/2-1-2-graphs-of-motion.md)
  - [2.1.3 Bouncing Ball Example](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/2-1-3-bouncing-ball-example.md)
  - [2.1.4 End of Topic Test - Motion in a Straight Line](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/2-1-4-end-of-topic-test-motion-in-a-straight-line.md)
  - [2.1.5 Acceleration Due to Gravity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/2-1-5-acceleration-due-to-gravity.md)

### 3 Dynamics
- 3.1 Momentum & Newton's Laws of Motion
  - [3.1.1 Mass & Inertia](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-1-1-mass-and-inertia.md)
  - [3.1.2 Newton's Laws](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-1-2-newtons-laws.md)
  - [3.1.3 Momentum](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-1-3-momentum.md)
  - [3.1.4 End of Topic Test - Newton's Laws & Momentum](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-1-4-end-of-topic-test-newtons-laws-and-momentum.md)
  - [3.1.5 A-A* (AO3/4) - Newton's Third Law](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-1-5-a-a-ao34-newtons-third-law.md)
- 3.2 Non-Uniform Motion
  - [3.2.1 Projectile Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-2-1-projectile-motion.md)
- 3.3 Linear Momentum & Conservation
  - [3.3.1 Conservation of Momentum](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/3-3-1-conservation-of-momentum.md)

### 4 Force, Density & Pressure
- 4.1 Force, Density & Pressure
  - [4.1.1 Fields](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-1-fields.md)
  - [4.1.2 Force in Uniform Fields](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-2-force-in-uniform-fields.md)
  - [4.1.3 Friction](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-3-friction.md)
  - [4.1.4 Buoyancy](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-4-buoyancy.md)
  - [4.1.5 Terminal Speed](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-5-terminal-speed.md)
  - [4.1.6 End of Topic Test - Acceleration Due to Gravity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-6-end-of-topic-test-acceleration-due-to-gravity.md)
  - [4.1.7 Centre of Mass](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-7-centre-of-mass.md)
  - [4.1.8 Forces & Equilibrium](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-8-forces-and-equilibrium.md)
  - [4.1.9 End of Topic Test - Scalars & Vectors](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-9-end-of-topic-test-scalars-and-vectors.md)
  - [4.1.10 Moments](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-10-moments.md)
  - [4.1.11 End of Topic Test - Moments & Centre of Mass](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-11-end-of-topic-test-moments-and-centre-of-mass.md)
  - [4.1.12 Density](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-12-density.md)
  - [4.1.13 Pressure](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/4-1-13-pressure.md)

### 5 Work, Energy & Power
- 5.1 Work, Energy & Power
  - [5.1.1 Work & Energy](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-1-1-work-and-energy.md)
  - [5.1.2 Power & Efficiency](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-1-2-power-and-efficiency.md)
  - [5.1.3 Conservation of Energy](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-1-3-conservation-of-energy.md)
  - [5.1.4 End of Topic Test - Work, Energy & Power](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-1-4-end-of-topic-test-work-energy-and-power.md)
- 5.2 Gravitational Fields
  - [5.2.1 Newton's Law](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-2-1-newtons-law.md)
  - [5.2.2 Gravitational Field Strength](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-2-2-gravitational-field-strength.md)
  - [5.2.3 Gravitational Potential](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/5-2-3-gravitational-potential.md)

### 6 Deformation of Solids
- 6.1 Materials
  - [6.1.1 Bulk Properties of Solids](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/6-1-1-bulk-properties-of-solids.md)
  - [6.1.2 Energy in Materials](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/6-1-2-energy-in-materials.md)
  - [6.1.3 Young Modulus](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/6-1-3-young-modulus.md)
  - [6.1.4 End of Topic Test - Materials](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/6-1-4-end-of-topic-test-materials.md)

### 7 Waves
- 7.1 Simple Harmonic Motion
  - [7.1.1 Simple Harmonic Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-1-simple-harmonic-motion.md)
  - [7.1.2 Simple Harmonic Systems](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-2-simple-harmonic-systems.md)
  - [7.1.3 Energy in Simple Harmonic Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-3-energy-in-simple-harmonic-motion.md)
  - [7.1.4 Resonance](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-4-resonance.md)
  - [7.1.5 End of Topic Test - Simple Harmonic Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-5-end-of-topic-test-simple-harmonic-motion.md)
  - [7.1.6 A-A* (AO3/4) - Simple Harmonic Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-6-a-a-ao34-simple-harmonic-motion.md)
  - [7.1.7 End of Topic Test - Gravitational Fields](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-1-7-end-of-topic-test-gravitational-fields.md)
- 7.2 Waves
  - [7.2.1 Progressive Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-1-progressive-waves.md)
  - [7.2.2 Intensity of Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-2-intensity-of-waves.md)
  - [7.2.3 Wave Speed & Phase Difference](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-3-wave-speed-and-phase-difference.md)
  - [7.2.4 Longitudinal & Transverse Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-4-longitudinal-and-transverse-waves.md)
  - [7.2.5 End of Topic Test - Progressive Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-5-end-of-topic-test-progressive-waves.md)
  - [7.2.6 Electromagnetic Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-6-electromagnetic-waves.md)
  - [7.2.7 Doppler Effect](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-7-doppler-effect.md)
  - [7.2.8 Sound Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-8-sound-waves.md)
  - [7.2.9 Measuring Sound Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-9-measuring-sound-waves.md)
  - [7.2.10 End of Topic Test - Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-10-end-of-topic-test-waves.md)
  - [7.2.11 Ultrasound Imaging](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-11-ultrasound-imaging.md)
  - [7.2.12 Ultrasound Imaging 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/7-2-12-ultrasound-imaging-2.md)

### 8 Superposition
- 8.1 Superposition
  - [8.1.1 Stationary Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-1-stationary-waves.md)
  - [8.1.2 Stationary Waves 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-2-stationary-waves-2.md)
  - [8.1.3 End of Topic Test - Stationary Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-3-end-of-topic-test-stationary-waves.md)
  - [8.1.4 A-A* (AO3/4) - Stationary Waves](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-4-a-a-ao34-stationary-waves.md)
  - [8.1.5 Interference](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-5-interference.md)
  - [8.1.6 Interference 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-6-interference-2.md)
  - [8.1.7 End of Topic Test - Interference](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-7-end-of-topic-test-interference.md)
  - [8.1.8 Diffraction](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-8-diffraction.md)
  - [8.1.9 Diffraction Gratings](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-9-diffraction-gratings.md)
  - [8.1.10 End of Topic Test - Diffraction](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/8-1-10-end-of-topic-test-diffraction.md)

### 9 Thermal Physics
- 9.1 Circular Motion
  - [9.1.1 Circular Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-1-1-circular-motion.md)
  - [9.1.2 Circular Motion 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-1-2-circular-motion-2.md)
  - [9.1.3 End of Topic Test - Circular Motion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-1-3-end-of-topic-test-circular-motion.md)
- 9.2 Thermal Physics
  - [9.2.1 Temperature](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-1-temperature.md)
  - [9.2.2 Measuring Temperature](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-2-measuring-temperature.md)
  - [9.2.3 Ideal Gas Law](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-3-ideal-gas-law.md)
  - [9.2.4 Ideal Gases](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-4-ideal-gases.md)
  - [9.2.5 Boyle's Law & Charles' Law](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-5-boyles-law-and-charles-law.md)
  - [9.2.6 Molecular Kinetic Theory Model](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-6-molecular-kinetic-theory-model.md)
  - [9.2.7 Molecular Kinetic Theory Model 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-7-molecular-kinetic-theory-model-2.md)
  - [9.2.8 Thermal Energy Transfer](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-8-thermal-energy-transfer.md)
  - [9.2.9 Thermal Energy Transfer Experiments](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-9-thermal-energy-transfer-experiments.md)
  - [9.2.10 End of Topic Test - Thermal Energy & Ideal Gases](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-10-end-of-topic-test-thermal-energy-and-ideal-gases.md)
  - [9.2.11 First Law of Thermodynamics](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/9-2-11-first-law-of-thermodynamics.md)

### 10 Communication
- 10.1 Communication Channels
  - [10.1.1 Communication Channels](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/10-1-1-communication-channels.md)
  - [10.1.2 Modulation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/10-1-2-modulation.md)
  - [10.1.3 Attenuation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/10-1-3-attenuation.md)
- 10.2 Digital Communication
  - [10.2.1 Digital & Analogue Signals](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/10-2-1-digital-and-analogue-signals.md)
  - [10.2.2 Representing Sound](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/10-2-2-representing-sound.md)

### 11 Electric Fields
- 11.1 Electric Fields
  - [11.1.1 Coulomb's Law](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-1-coulombs-law.md)
  - [11.1.2 Electric Field Strength](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-2-electric-field-strength.md)
  - [11.1.3 Electric Field Strength 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-3-electric-field-strength-2.md)
  - [11.1.4 Electric Potential](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-4-electric-potential.md)
  - [11.1.5 End of Topic Test - Electric Fields](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-5-end-of-topic-test-electric-fields.md)
  - [11.1.6 A-A* (AO3/4) - Electric and Gravitational Field](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-1-6-a-a-ao34-electric-and-gravitational-field.md)
- 11.2 Capacitance
  - [11.2.1 Capacitance](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-2-1-capacitance.md)
  - [11.2.2 Parallel Plate Capacitor](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-2-2-parallel-plate-capacitor.md)
  - [11.2.3 Energy Stored by a Capacitor](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-2-3-energy-stored-by-a-capacitor.md)
  - [11.2.4 Capacitor Discharge](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-2-4-capacitor-discharge.md)
  - [11.2.5 Capacitor Charge](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/11-2-5-capacitor-charge.md)

### 12 Current Electricity
- 12.1 Current Electricity
  - [12.1.1 Basics of Electricity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-1-basics-of-electricity.md)
  - [12.1.2 Mean Drift Velocity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-2-mean-drift-velocity.md)
  - [12.1.3 Current-Voltage Characteristics](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-3-current-voltage-characteristics.md)
  - [12.1.4 End of Topic Test - Basics of Electricity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-4-end-of-topic-test-basics-of-electricity.md)
  - [12.1.5 Resistivity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-5-resistivity.md)
  - [12.1.6 End of Topic Test - Resistivity & Superconductors](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-6-end-of-topic-test-resistivity-and-superconductors.md)
  - [12.1.7 Power and Conservation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-7-power-and-conservation.md)
  - [12.1.8 Microphones](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-8-microphones.md)
  - [12.1.9 Components](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-9-components.md)
  - [12.1.10 Relays](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-10-relays.md)
  - [12.1.11 Strain Gauges](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-1-11-strain-gauges.md)
- 12.2 DC Circuits
  - [12.2.1 Circuits](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-2-1-circuits.md)
  - [12.2.2 Potential Divider](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-2-2-potential-divider.md)
  - [12.2.3 Emf & Internal Resistance](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-2-3-emf-and-internal-resistance.md)
  - [12.2.4 End of Topic Test - Power & Potential](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/12-2-4-end-of-topic-test-power-and-potential.md)

### 13 Magnetic Fields
- 13.1 Magnetic Fields
  - [13.1.1 Magnetic Flux Density](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-1-magnetic-flux-density.md)
  - [13.1.2 End of Topic Test - Capacitance & Flux Density](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-2-end-of-topic-test-capacitance-and-flux-density.md)
  - [13.1.3 Moving Charges in a Magnetic Field](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-3-moving-charges-in-a-magnetic-field.md)
  - [13.1.4 Magnetic Flux & Flux Linkage](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-4-magnetic-flux-and-flux-linkage.md)
  - [13.1.5 Electromagnetic Induction](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-5-electromagnetic-induction.md)
  - [13.1.6 Electromagnetic Induction 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-6-electromagnetic-induction-2.md)
  - [13.1.7 Magnetic Flux Density](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-7-magnetic-flux-density.md)
  - [13.1.8 Magnetic Resonance Scanning](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-1-8-magnetic-resonance-scanning.md)
- 13.2 Alternating Currents
  - [13.2.1 Alternating Currents](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-2-1-alternating-currents.md)
  - [13.2.2 Operation of a Transformer](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-2-2-operation-of-a-transformer.md)
  - [13.2.3 End of Topic Test - Electromagnetic Induction & AC](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-2-3-end-of-topic-test-electromagnetic-induction-and-ac.md)
  - [13.2.4 Rectification](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/13-2-4-rectification.md)

### 14 Modern Physics
- 14.1 Quantum Physics
  - [14.1.1 The Photoelectric Effect](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-1-the-photoelectric-effect.md)
  - [14.1.2 The Photoelectric Effect Explanation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-2-the-photoelectric-effect-explanation.md)
  - [14.1.3 End of Topic Test - The Photoelectric Effect](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-3-end-of-topic-test-the-photoelectric-effect.md)
  - [14.1.4 Collisions of Electrons with Atoms](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-4-collisions-of-electrons-with-atoms.md)
  - [14.1.5 Energy Levels & Photon Emission](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-5-energy-levels-and-photon-emission.md)
  - [14.1.6 Wave-Particle Duality](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-6-wave-particle-duality.md)
  - [14.1.7 End of Topic Test - Absorption & Emission](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-7-end-of-topic-test-absorption-and-emission.md)
  - [14.1.8 Band Theory](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-8-band-theory.md)
  - [14.1.9 Diagnostic X-Rays](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-9-diagnostic-x-rays.md)
  - [14.1.10 X-Ray Image Processing](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-10-x-ray-image-processing.md)
  - [14.1.11 Absorption of X-Rays](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-11-absorption-of-x-rays.md)
  - [14.1.12 CT Scanners](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-1-12-ct-scanners.md)
- 14.2 Nuclear Physics
  - [14.2.1 Rutherford Scattering](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-1-rutherford-scattering.md)
  - [14.2.2 Atomic Model](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-2-atomic-model.md)
  - [14.2.3 Isotopes](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-3-isotopes.md)
  - [14.2.4 Stable & Unstable Nuclei](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-4-stable-and-unstable-nuclei.md)
  - [14.2.5 A-A* (AO3/4) - Stable & Unstable Nuclei](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-5-a-a-ao34-stable-and-unstable-nuclei.md)
  - [14.2.6 Alpha & Beta Radiation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-6-alpha-and-beta-radiation.md)
  - [14.2.7 Gamma Radiation](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-7-gamma-radiation.md)
  - [14.2.8 Particles, Antiparticles & Photons](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-8-particles-antiparticles-and-photons.md)
  - [14.2.9 Quarks & Antiquarks](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-9-quarks-and-antiquarks.md)
  - [14.2.10 Particle Interactions](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-10-particle-interactions.md)
  - [14.2.11 Radioactive Decay](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-11-radioactive-decay.md)
  - [14.2.12 Half Life](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-12-half-life.md)
  - [14.2.13 End of Topic Test - Radioactivity](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-13-end-of-topic-test-radioactivity.md)
  - [14.2.14 Nuclear Instability](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-14-nuclear-instability.md)
  - [14.2.15 Mass & Energy](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-15-mass-and-energy.md)
  - [14.2.16 Binding Energy](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-16-binding-energy.md)
  - [14.2.17 A-A* (AO3/4) - Nuclear Fusion](https://senecalearning.com/en-gb/revision-notes/international-a-level/physics/cambridge-international/14-2-17-a-a-ao34-nuclear-fusion.md)