Science 7–10 · Year 9

Sound is a vibration: tuning fork in water and dancing sprinkles

Physical sciences — Waves and motion: waves, sound and light (NSW Stage 5 focus area)

PracticalLow risk

The idea

Every sound comes from a vibrating source, and the vibration passes through the air to make other objects vibrate.

What you need

tuning forks 256 Hz and 512 Hz, 1 each
rubber striking pad, 1
250 mL beaker two-thirds full of water, 1
bowl with cling film stretched tightly over the top, 1
hundreds-and-thousands sprinkles, a pinch
metal baking tray and a wooden spoon, 1 each
table-tennis ball on a thread, 1

How to do it

Before each step, predict what will happen and write down the reason.
Strike the 256 Hz fork on the pad, hold it close to the ear, then touch its prongs lightly to the water surface; observe.
Strike the fork again and hold a prong just touching the hanging table-tennis ball; observe.
Sprinkle sprinkles onto the cling film. Hold the baking tray 10 cm away without touching and strike it hard with the spoon; observe the sprinkles. Repeat softly and then from 50 cm.
Repeat step 2 with the 512 Hz fork and describe the difference in the sound.
Write a short explanation for each step that names the source, the medium and the detector.

What you should see

The water sprays droplets and ripples the instant the prongs touch it; the table-tennis ball is knocked away repeatedly; the sprinkles jump on the cling film when the tray is struck, higher for a louder strike and less at 50 cm, and not at all if the tray is struck softly at a distance. The 512 Hz fork sounds an octave higher. The learner knows it worked when the sprinkles jump with the tray untouched.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Sound is a substance that travels from the source.
Only loud sounds involve vibration.
A tuning fork makes sound without moving.

Safety card

Low riskLearners carry it out

Hazards

loud tray strike near ears
water spray on electrical equipment

Controls

strike away from faces
keep meters and phones dry

Note

No hazardous chemicals or naked flames are used. Complete the school's risk assessment for the activity before the lesson; the NSW Department of Education Science safety and compliance page points to CSIS 1.7 (Risk assessment – a pre-requisite for risk control) for how to carry it out.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC5-WAM-01 SC5-WS-01 SC5-WS-02 SC5-WS-08
Australian Curriculum v9AC9S9U04AC9S9I01AC9S9I08

Sources

The pages the author read to write this activity.

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