Track wave energy without carrying the medium along
Follow a disturbance and a marked part of its medium as two different motions.
Cross-referenced from the related Cambridge IGCSE Chemistry 0620 or Physics 0625 teaching to the 0652 syllabus. Exact 0652 Core/Supplement objective coverage and this final-series course’s examiner fit still need specialist review. Written practice is self-checked and does not predict a Cambridge grade or demonstrate supervised laboratory competence.
Before you begin
- Distinguish an object's motion from a changing pattern.
- Recognise energy transfer between locations.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
A marker rises and falls at the same horizontal location while a pulse moves right. Which motion is local?
What you will learn
- Know that waves transfer energy without transferring matter along with the wave.
- Distinguish local oscillation from the travelling pattern.
The disturbance travels while a marker stays local
A pulse moving along an ideal stretched rope passes successive parts of the rope. A marked part rises and falls near its original position while the disturbance travels along the rope. Energy can reach a distant part, even though the same piece of rope has not travelled there. Use that difference to explain wave transfer, rather than treating the moving shape as a transported lump of rope.
In a simple wave model, each part of a material medium oscillates locally. The wave propagates through successive interactions. Electromagnetic waves also transfer energy and do not require a material medium at all. The general energy-transfer statement is not a requirement that every kind of wave must have rope-like particles.
Interpret the observations within their conditions
The supplied snapshots label the same rope marker at one horizontal position while the pulse changes position. The marker's displacement changes; its identity and local reference position remain the same. Its vibration speed is not the pulse's propagation speed. The drawing is a qualitative teaching model, not measured motion or a model of every real water surface.
Currents, large-amplitude effects or other imposed motion can transport material in real situations. That does not justify identifying ordinary wave propagation with bulk transport of the medium in this school model. A floating object that drifts because of a separate current needs a separate account; a wave crest alone is not a tagged parcel of water.
Sources for this lesson
Pause and explain
Which statement expresses the selected wave-transfer model?
Worked example
A rope pulse moves 1.2 m right while a marked point moves up and down near its original horizontal location. What moves along the rope?
Show the worked solution
- The travelling disturbance changes horizontal position.
- The marked material point oscillates locally.
- Energy travels with the disturbance, rather than the marked rope point travelling 1.2 m.
Answer The disturbance and energy propagate; the marked medium oscillates locally.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain the difference between a rope pulse travelling right and a marked rope point rising and falling.
Give me a hint
Name the pattern and material motions separately.
Compare my reasoning
- The pulse changes position along the rope.
- The marked point oscillates near its reference location.
- Energy can propagate without that point moving along the whole path.
Travelling disturbance; local medium oscillation.
Look for these in your work
- Identify both motions.
- Link propagation to energy transfer.
A disturbance passes markers A, B and C in order. Does this show that marker A became marker C?
Give me a hint
Keep the identity of each material point separate from the pattern.
Compare my reasoning
- A, B and C are different parts of the medium.
- Each responds locally as the disturbance arrives.
- Sequential response is not transport of A into C.
No; successive material points respond to a travelling disturbance.
Look for these in your work
- Retain each marker's identity.
- Avoid treating the wave as a parcel.
A float drifts in a water current while ripples pass. Can all its drift be attributed to the ideal wave model?
Give me a hint
There is also a stated bulk flow.
Compare my reasoning
- The current can transport water and a float.
- Ripples are a travelling wave pattern.
- Separate current-driven drift from the local-oscillation account.
No; the imposed current needs a separate material-transport account.
Look for these in your work
- Identify the additional process.
- Keep the model's scope explicit.
Common mistakes
- A crest is a feature, not a tagged material parcel.
- Particle vibration speed is not wave speed.
- Separate an imposed current from the school wave model.
What can you explain now?
Does a pulse reaching the other end require the same rope particle to arrive there?
Compare with the explanation
No.
Successive local interactions transfer the disturbance and energy.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain wave propagation with a local marker and distinguish energy transfer from bulk material transport.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.