OCR · A-Level · Physics
Course version: H556 · Version from Sept 2015
(f) the idea that the separation between adjacent nodes (or antinodes) is…
Full specification wording
Stationary waves: (f) the idea that the separation between adjacent nodes (or antinodes) is equal to /2 m , where m is the wavelength of the progressive wave
A stationary wave forms when two progressive waves of the same frequency and similar amplitude travel in opposite directions through the same medium.
Checked against the OCR H556 specification (opens in a new tab) on .
- Point 7 of 8
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A stationary wave forms when two progressive waves of the same frequency and similar amplitude travel in opposite directions through the same medium. The pattern has fixed nodes, where displacement is always zero, and antinodes, where displacement varies with maximum amplitude. The key relationship is that the distance between one node and the next node is half a wavelength, λ/2. The same spacing applies between adjacent antinodes. For example, if a microwave stationary wave has nodes 1.5 cm apart, then λ/2 = 1.5 cm, so λ = 3.0 cm. This spacing arises because the wave must travel one full wavelength to return to the same phase, and a node-to-node path corresponds to half that cycle.
What earns the marks
- States that the separation between adjacent nodes is λ/2.
- States that the separation between adjacent antinodes is also λ/2.
- Explains that a stationary wave is formed by two progressive waves of the same frequency travelling in opposite directions.
- Uses the relationship λ = 2 × (node separation) to calculate wavelength.
- Recognises that nodes are points of zero displacement and antinodes are points of maximum displacement.
Common mistakes and how to put them right
Confusing node separation with a full wavelength.
Put it right: The distance between adjacent nodes is λ/2, not λ.
Thinking that the distance from a node to the next antinode is λ/2.
Put it right: It is actually λ/4.
Assuming that all points between nodes vibrate with the same amplitude.
Put it right: Amplitude varies from zero at nodes to maximum at antinodes.
Measuring only one node spacing and treating it as the wavelength without doubling.
Exam tips
- Sketch the stationary wave pattern and label nodes and antinodes before substituting values.
- If a question gives the distance between the first and fifth node, count the number of half-wavelength intervals (four) and divide accordingly.
- Check units carefully: convert cm to m before calculating wavelength in metres.
- Use the phrase 'adjacent nodes are separated by half a wavelength' in explanations to secure the mark.
Try the lesson
The start of the Stationary waves: (f) the idea that the separation between adjacent nodes (or antinodes) is equal to /2 m , where m is the wavelength of the progressive wave lesson, made from checked teaching notes for this specification point.
Listen
A stationary wave forms when two progressive waves of the same frequency and similar amplitude travel in opposite directions through the same medium. The pattern has fixed nodes, where displacement is always zero, and antinodes, where displacement varies with maximum amplitude. The key relationship is that the distance between one node and the next node is half a wavelength, λ/2. The same spacing applies between adjacent antinodes. For example, if a microwave stationary wave has nodes 1.5 cm apart, then λ/2 = 1.5 cm, so λ = 3.0 cm. This spacing arises because the wave must travel one full wavelength to return to the same phase, and a node-to-node path corresponds to half that cycle. A strong answer earns marks for these points. States that the separation between adjacent nodes is λ/2. States that the separation between adjacent antinodes is also λ/2. Explains that a stationary wave is formed by two progressive waves of the same frequency travelling in opposite directions. Uses the relationship λ = 2 × (node separation) to calculate wavelength. Exam tip: Sketch the stationary wave pattern and label nodes and antinodes before substituting values.
Key words
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Stationary wave formation
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Node and antinode spacing
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Wavelength determination
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See every definition
- Stationary wave formation
- A stationary wave forms when two progressive waves of the same frequency and similar amplitude travel in opposite directions through the same medium.
- Node and antinode spacing
- The separation between adjacent nodes, or between adjacent antinodes, is equal to half a wavelength.
- Wavelength determination
- The wavelength is found using the relationship λ = 2 × (node separation), measuring across several node spacings and dividing to reduce uncertainty.
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