lesson
Sound transfers a disturbance through matter
1 · Learn
Sound is produced by vibrations and travels through a medium as a longitudinal wave. Particles oscillate about positions while the disturbance and energy move onwards. Sound does not travel through a vacuum because there is no material medium for this process.
Frequency is oscillations per second, measured in hertz, and relates to pitch. Amplitude relates to loudness but is not the same quantity as frequency. Do not test sound by using uncomfortable volumes.
2 · Worked example
A higher-frequency tone has a higher pitch in the comparison. Making the same-frequency tone larger in amplitude changes loudness rather than automatically raising pitch.
3 · Your turn
What changes when the frequency rises while the comparison's amplitude is held constant?
Check your answer
Pitch rises; amplitude has not been increased in the stated comparison.
4 · Apply your learning
Read two supplied wave diagrams and distinguish a frequency change from an amplitude change.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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