HOME PAGE * SEARCH * UK KS3 level Science Quizzes for students aged ~13-14

UK GCSE level Biology * Chemistry * Physics ~14-16 * Advanced Level Chemistry ~16-18

School-college Physics Notes: Waves 9. Wave diffraction model of waves

GCSE level Physics exam revision notes on waves

Introduction to waves: 9. DIFFRACTION of waves and a scientific wave model diagram, examples of diffraction described and explained

[Author © Dr Phil Brown PhD: Doc Brown's physics exam revision notes suitable for students of UK IGCSE & GCSE level physics courses, ~ US grades 9-10 physics [waves-intro- page updated Mar 31st 2026 *]

 email doc brown: problems?, comments? query? * [privacy & cookies policies & disclaimer]

[KEY POINTS and learning objectives for this page, after initial notes]

INDEX physics notes: Investigating & introducing properties of waves

9. DIFFRACTION of waves and a scientific wave model - Mind the gap !!!

Theoretical model of a diffracted wave.

  • The scientific model of the diffraction of waves through a gap (or bending round a corner)

  • Diffraction is the effect of waves spreading out when passing through a gap or passing by a barrier. In effect, waves go round corners! and it doesn't matter if its sound, light or water waves - they all diffract and bend round corners! The effect is so small with light (tiny wavelength), you don't notice it, but you see water waves bending around the walls of a harbour and you can hear sounds from round a corner.

  • You should appreciate that significant diffraction only occurs when the wavelength of the wave is of the same order of magnitude as the size of the gap or obstacle.

  • A: There is a relatively small diffraction effect when waves pass through a wide gap that is much bigger than the wavelength of the wave.

  • B: You get the maximum spreading or diffraction when the waves pass through a gap of similar size to the wavelength of the incident waves.

  • You can see these effects with transverse water waves at the seaside as waves hit the protective walls of a harbour BUT you need a very tiny slit to observe diffraction with light waves because of their tiny wavelength.

  • Excluding satellite TV and radio, if it wasn't for diffraction you would never get a radio signal down in a valley - the radio waves bend over the hills!

INDEX notes: Investigating and introducing the properties of waves

Key points Introduction to waves: A model of wave of diffraction through a gap

Information sources for Doc Brown's key points: IGCSE-GCSE physics are based on textbooks & syllabus-specifications for students taking the UK AQA, Edexcel, OCR 21st Century Science, OCR Gateway science suite, WJEC, CCEA and CIE GCSE physics 9-1 level science examinations

Here's a structured set of summary revision notes on a model to explain the diffraction of waves at a gap, aligned with the core requirements across major UK GCSE/IGCSE exam boards (WJEC, CCEA, CIE, AQA, Edexcel, OCR). This model helps students visualise how waves spread when encountering obstacles or openings - essential for mastering wave behaviour.

Diffraction of Waves at a Gap: Conceptual Model

Definition: Diffraction is the spreading out of waves when they pass through a gap or move around an obstacle.

It occurs with all wave types, including sound, light, water, and electromagnetic waves.

Diffraction Model Components

Component Description
Wavefronts Lines representing the crests of transverse waves or compressions of longitudinal waves
Gap size Determines the extent of diffraction - maximum when gap ≈ wavelength
Direction change Waves bend and spread out after passing through the gap
Amplitude May decrease due to energy spreading
Wavelength Remains constant during diffraction

Required Diffraction Practical (Ripple Tank)

Students investigate diffraction by:

  • Generating water waves with a vibrating bar
  • Passing waves through narrow and wide gaps
  • Observing wavefront curvature and spreading
  • Comparing diffraction for different wavelengths

Real-World Examples of Diffraction

  • Sound bending around corners or through doorways
  • Water waves spreading after passing through harbour entrances
  • Radio waves diffracting around buildings
  • Light diffracting through narrow slits (less noticeable due to short wavelength)

Typical Exam Board Coverage of the diffraction model

Diffraction Model Required Practical
 Wavefronts and gap size  Ripple tank diffraction
 Diffraction of sound/light  Water wave experiments
 Wave behaviour at gaps  Ripple tank setup
 Diffraction in water/sound  Wave tank observations
 Diffraction of sound/light  Sound wave experiments
 Diffraction and wavefronts  Ripple tank & slit experiments

 Student Tips about diffraction

  • Use wavefront diagrams to show how waves bend at gaps.
  • Remember: diffraction is most noticeable when wavelength ≈ gap size.
  • Practise identifying diffraction in real-world contexts (e.g. sound around corners).
  • Link diffraction to communication technologies (e.g. radio signals).
  • Review required practicals to reinforce theory with visual evidence.

Common Misconceptions about diffraction

  •  “Diffraction only happens with sound.”
     All waves can diffract - light, water, and EM waves included.
  •  “Waves change speed during diffraction.”
     Speed and wavelength stay constant; only direction changes.
  •  “Diffraction only occurs at sharp edges.”
     It occurs at any gap or obstacle, depending on wave properties.
  •  “Smaller gaps always cause more diffraction.”
     Only when the gap size is similar to the wavelength.

Keywords, phrases and learning objectives for the diffraction model of waves

Be able to describe diffraction of waves using a scientific wave model and explain wave diffraction with suitable diagrams i.e. explain the theoretical modelling of diffracted waves.

Website content © Dr Phil Brown 2000+. All copyrights reserved on Doc Brown's physics revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries and references to science course specifications are unofficial. Explaining the importance of scientific model of diffraction, examples explained in GCSE physics, What you need to know about scientific model of diffraction, examples explained for IGCSE physics, Explaining the use of scientific model of diffraction, examples explained knowledge in GCSE physics, Examples of scientific model of diffraction, examples explained for GCSE physics exams, What is the significance of scientific model of diffraction, examples explained in studying for physics exams, What is the use of scientific model of diffraction, examples explained ?  Describing and explaining the theory of scientific model of diffraction, examples explained, revision preparation for AQA GCSE physics, Edexcel GCSE physics, OCR GCSE physics. Website content © Dr Phil Brown 2000+. All copyrights reserved on Doc Brown's physics revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries and references to science course specifications are unofficial. These revision notes on scientific model of diffraction, examples explained are suitable for AQA gcse physics, scientific model of diffraction, examples explained revision notes for Edexcel gcse physics, scientific model of diffraction, examples explained revision notes for OCR gcse Gateway science physics, scientific model of diffraction, examples explained revision notes for OCR 21st Century science physics, scientific model of diffraction, examples explained revision notes WJEC GCSE physics, scientific model of diffraction, examples explained revision notes for CCEA gcse physics, scientific model of diffraction, examples explained revision notes for CIE Cambridge IGCSE physics exams.  scientific model of diffraction, examples explained with examples, help in revising scientific model of diffraction, examples explained for gcse physics exams, knowing the importance of scientific model of diffraction, examples explained for gcse physics exams, key points to know about scientific model of diffraction, examples explained, exam revision notes for scientific model of diffraction, examples explained, what you need to know about scientific model of diffraction, examples explained, revision help in learning about scientific model of diffraction, examples explained, importance of diagram of scientific model describing wave refraction in GCSE level physics, What you need to know about diagram of scientific model describing wave refraction for GCSE level physics, Explaining the use of diagram of scientific model describing wave refraction knowledge in GCSE level physics, Examples of diagram of scientific model describing wave refraction explained when studying GCSE level physics, What is significant about diagram of scientific model describing wave refraction, describing the theory of diagram of scientific model describing wave refraction when studying GCSE level physics, revision notes for diagram of scientific model describing wave refraction in exams, online exam help for diagram of scientific model describing wave refraction, revision notes about diagram of scientific model describing wave refraction, what do I need to learn about diagram of scientific model describing wave refraction for by GCSE physics exam? help to understand the diagram of scientific model describing wave refraction topic in preparation for GCSE physics exam question, how to prepare for questions involving diagram of scientific model describing wave refraction in a GCSE physics examination? Revision notes on diagram of scientific model describing wave refraction based on the syllabus-specifications for students taking IGCSE/GCSE level physics examinations, summary revision notes and key points on diagram of scientific model describing wave refraction for students taking the AQA igcse/gcse physics notes on diagram of scientific model describing wave refraction, Edexcel gcse physics notes on diagram of scientific model describing wave refraction,  OCR 21st century GCSE physics notes on diagram of scientific model describing wave refraction, OCR gateway GCSE physics notes on diagram of scientific model describing wave refraction, WJEC gcse physics notes on diagram of scientific model describing wave refraction, CCEA gcse physics notes on diagram of scientific model describing wave refraction for students taking CIE Cambridge igcse physics, exam revision notes on diagram of scientific model describing wave refraction, useful for US grade 9-10 physics courses

TOP OF PAGE