This topic summary covers Knowledge Organiser: Sound Waves within Sound Waves for GCSE Physics. Revise Sound Waves in Waves for GCSE Physics with 13 exam-style questions and 15 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 13 of 13 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Sound Waves
Key Terms
- Longitudinal: particles vibrate parallel to wave travel
- Compression: high-pressure region
- Rarefaction: low-pressure region
- Ultrasound: frequency > 20,000 Hz
- Infrasound: frequency < 20 Hz
Key Facts
- Sound speed: gas < liquid < solid
- Sound in air: ~330 m/s
- Cannot travel through vacuum
- Louder = bigger amplitude on oscilloscope
- Higher pitch = higher frequency on oscilloscope
Key Equations
- v = f × λ
- distance = (speed × time) ÷ 2 (echo)
- f = 1/T
Exam Tips
- Echo formula: always ÷2 for return journey
- Ultrasound = non-ionising = safe for foetuses
- Sound = longitudinal; EM waves = transverse
- Amplitude affects loudness; frequency affects pitch
Common Mistakes
- Forgetting to halve in echo calculations: The measured time is for the sound to travel to the object AND back — divide by 2 before multiplying by speed to get the one-way distance
- Saying sound travels faster in air than solids: Sound travels fastest in solids, then liquids, then slowest in gases — denser packing means vibrations transfer more efficiently
- Confusing amplitude and frequency effects: Amplitude determines loudness (volume); frequency determines pitch — a louder sound has larger amplitude, not higher frequency
- Saying sound is a transverse wave: Sound is a longitudinal wave — particles vibrate parallel to the direction of wave travel, creating compressions and rarefactions
- Saying ultrasound is ionising: Ultrasound is non-ionising — it is safe for medical imaging including foetal scans; X-rays are ionising and have associated risks
Practice questions for Sound Waves
What type of wave is sound?
Describe how a sound wave is produced and how energy is transferred by a longitudinal wave.
Quick recall flashcards
Sound wave type?
Longitudinal
What is an echo?
Reflection of sound waves from a surface