Follow heating and wave energy transfers
Explain transfer by temperature difference and by electromagnetic, sound and other waves.
Exam scope and assessment notes
Core and Extended · Physics 0625, 2026–2028, section 1.7.1. Energy stores, transfers and simple conservation are Core; kinetic and gravitational potential energy equations, multistage conservation and Sankey diagrams are Supplement. State the system, interval and model assumptions. Written practice is self-checked. Supervised practical experience, cumulative assessment and human subject-teacher review remain pending.
Before you begin
- Name an internal energy store.
- Distinguish stores from transfers.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which phrase names a store in a hot cup?
What you will learn
- Describe energy transferred by heating.
- Recognise waves as energy-transfer pathways.
Heating describes transfer between systems
Energy can transfer by heating because of a temperature difference. A hot cup and cooler room can exchange energy so the cup's internal store decreases and the surroundings' internal store increases. The direction of net thermal transfer in this simple account is from hotter to cooler. 'Heat stored in the cup' is less precise here than an internal store and a transfer by heating.
Heating can occur by conduction, convection and radiation; later thermal lessons examine those mechanisms. Electromagnetic radiation is also a wave pathway, so one radiation event should not be added twice to an energy budget because it fits two descriptive categories. Absorbed sunlight can increase internal stores or drive chemical changes; a wave arriving is not proof that every joule is absorbed.
Waves carry energy without bulk transport of the medium
Electromagnetic waves, including visible light and infrared, can transfer energy through vacuum. Sound waves transfer energy through a material medium. Water and other mechanical waves can also transfer energy while local particles oscillate rather than all travelling with the wave across the whole distance. Energy can reach a detector even when the material's average position stays nearly unchanged.
A loudspeaker transfers energy by sound and can also warm itself and its surroundings. Some incident wave energy can be reflected or transmitted instead of being absorbed into a receiver's store. A clear account names the source, receiver and relevant wave pathway, and distinguishes an energy transfer from a claim that the medium or every particle moved from source to receiver.
Pause and explain
Must water travel all the way from a wave source to a distant receiver for wave energy to arrive?
Worked example
Describe an infrared wave from a warmer source absorbed by a cooler surface.
Show the worked solution
- The source transfers energy by electromagnetic radiation.
- The absorbed energy increases the receiver's internal store.
- Count that wave transfer once rather than separately adding an identical heating amount.
Answer Electromagnetic-wave transfer increases the receiver's internal store; count the transfer once.
Try a topic test
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 energy account for infrared absorbed by a cooler surface from a warmer source.
Give me a hint
Name the wave pathway and the receiver's store.
Compare my reasoning
- Infrared is an electromagnetic wave.
- Absorbed radiation transfers energy to the surface.
- The receiver's internal store increases.
Electromagnetic radiation transfers energy into the receiver's internal store.
Look for these in your work
- Use an electromagnetic pathway.
- Identify absorption rather than assuming all incident radiation enters the store.
Compare sound from a speaker, visible light through vacuum and a water wave reaching a floating detector.
Give me a hint
Identify the pathways and which need a material medium.
Compare my reasoning
- Sound transfers energy through a material medium.
- Visible electromagnetic radiation can transfer energy through vacuum.
- The water wave transfers energy through local oscillations without requiring all water to reach the detector.
Sound, electromagnetic and water-wave transfers; sound and water waves need their material media.
Look for these in your work
- Include all three wave examples.
- Separate propagation from bulk transport.
A budget lists 30 J received as infrared radiation and then adds another 30 J for heating by that same radiation. Correct the accounting.
Give me a hint
Ask whether the entries describe two distinct physical transfers.
Compare my reasoning
- Both labels refer to the same absorption event.
- Only 30 J is supplied by that stated event.
- Do not count it twice merely because radiation can be discussed as heating and as an electromagnetic pathway.
Count 30 J once, not 60 J, for the same radiation event.
Look for these in your work
- Recognise the identical event.
- Preserve a single energy budget.
Common mistakes
- Internal energy is stored; heating is a transfer.
- Do not double-count radiation.
- A wave transfer need not transport the medium bodily to the receiver.
What can you explain now?
Can electromagnetic waves transfer energy through vacuum?
Compare with the explanation
Yes.
Unlike sound, electromagnetic waves do not require a material medium.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Contrast heating and internal energy, and explain how light, sound and water waves transfer energy.
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.