Diffraction
Diffraction is the spreading out of waves as they pass through a gap or around an obstacle.
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Diffraction is the spreading out of waves as they pass through a gap or around an obstacle.
- Most noticeable when the gap matches the wavelength
- Explains hearing around corners
- Wavelength does not change
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Diffraction?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Diffraction. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Diffraction in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Diffraction explains how the physical world behaves, from sport and transport to electricity and medicine.
Diffraction in detail
Diffraction is the spreading out of waves when they pass through a gap or around an obstacle. It is greatest when the gap width is about the same as the wavelength, and little diffraction occurs when the gap is much larger.
This is why you can hear someone around a corner (sound has long wavelengths of about a metre) but cannot see them (light wavelengths are about 500 nm). Diffraction also limits the sharpness of images in telescopes and microscopes, and it is evidence that light behaves as a wave.
How the interactive helps you understand Diffraction
Watch the wave in the interactive. Use any sliders or buttons it offers to change the values and see how the wave responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Diffraction.
Real-life uses and examples
- Answer “explain” questions by linking Diffraction to a clear cause and effect.
- Predict what a ball, car or circuit will do with Diffraction before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Diffraction.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Diffraction with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Diffraction
What is Diffraction?
Diffraction is the spreading out of waves as they pass through a gap or around an obstacle.
What are the most important points about Diffraction?
The main points are: Most noticeable when the gap matches the wavelength; Explains hearing around corners; Wavelength does not change.
Why is Diffraction useful?
Understanding Diffraction explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Diffraction?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Diffraction?
Related topics in Physics include Pitch, Loudness and Echoes, Refraction of Light, The Human Eye and Vision.