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Propagation of Sound

Propagation of sound is the travelling of sound energy through a material medium by successive compressions and rarefactions.

Practice This Concept

Main explanation

Teacher explanation

Sound cannot travel in vacuum because it needs particles of a medium to pass the disturbance. In air, vibrating particles push nearby particles closer to form compressions, then move back to form rarefactions. The particles only vibrate about their positions, while the sound disturbance travels forward.

Example

A ringing bell inside a jar becomes faint when air is removed because fewer air particles are available to carry the sound.

Simple analogy

Particles vibrate; sound travels.

Common confusion

Students often say air particles travel from the bell to the ear. Actually, particles vibrate locally while energy travels.

Exam tip

For propagation answers, include three words: medium, compression, rarefaction.

Study the propagation of sound diagram carefully

Use the labelled diagram to keep propagation of sound clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of propagation of sound in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on propagation of sound.

Revision cue

Revise propagation of sound through the labels before writing the answer.

Answer writing and exam use

1-mark use

Write the exact meaning of propagation of sound in one clean line.

2-mark use

Define propagation of sound and add one example or condition.

3-mark use

Explain propagation of sound, show the method or example, and mention the common mistake.

MCQ Quiz

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