Cambridge IGCSE Physics Notes 3.4: Sound
Cambridge IGCSE Physics sound notes on longitudinal waves, compression, frequency, pitch, amplitude, loudness, echoes, and speed measurement.
Q: What does Cambridge IGCSE Physics Notes 3.4: Sound cover?
A: It follows official Cambridge Physics section 3.4 for syllabuses 0625 and 0972, with Core ideas separated from Supplement depth.
Sound is a longitudinal mechanical wave whose frequency determines pitch and whose amplitude relates to loudness.
The ideas that organise this section
- Sound needs a medium because it is transmitted through particle vibrations.
- Frequency and amplitude describe different perceptions: pitch and loudness.
- Echo timing measures a round trip, so the one-way distance is half the total path.
Core route
Core candidates should be ready to describe, calculate, interpret, and apply the following:
- Describe compressions and rarefactions and identify sound as longitudinal.
- Relate frequency to pitch and amplitude to loudness.
- Use echo or direct-timing methods to determine sound speed.
Supplement route
Extended candidates study all Core content and add the following depth:
- Interpret oscilloscope traces for relative frequency and amplitude.
- Explain why sound speed differs between media using particle interactions.
- Apply reflection and ultrasound principles to measurement or imaging contexts.
Formula route
- Relationship: speed = distance / time.
- Relationship: frequency = 1 / period.
Write the relationship before substituting. Convert units first, keep extra figures during working, and round only the final answer to sensible precision.
Build a connected model
In Sound, a strong answer connects the named quantity or model to observable evidence. Begin by defining the physical quantity in words or with its relationship. Identify which values are scalars and which require a direction. Represent the situation with a labelled diagram, graph, field pattern, ray or circuit when that makes the relationship visible. The representation is part of the reasoning: its labels, arrows and scale should agree with the written explanation.
For a calculation, write the governing relationship before substitution, convert prefixes and time units, keep unrounded values during working and attach the correct final unit. For a qualitative question, use a cause-link-consequence chain. Name what changes, state the physical mechanism that links the change to the system, and then give the measurable result. If two cases are compared, hold unrelated variables constant and use the same physical principle for both.
