Ultrasound's practical applications

Steps:

• Recall ultrasound is sound waves above 20 kHz, used in non-audible applications like medical imaging and cleaning.
• Evaluate options: Identify which involves high-frequency vibrations for practical purposes.
• Match cleaning jewellery to ultrasonic cleaners, which use cavitation from ultrasound.
• Eliminate unrelated technologies like light-based or electrical ones.

Why A is correct:

• Ultrasound generates cavitation bubbles in liquids that implode to remove dirt from jewellery surfaces, as per the principle of acoustic cavitation in high-frequency sound waves.

Why the others are wrong:

• B: Fluorescent tubes use electrical discharge to produce visible light, not sound waves.
• C: Optical fibres transmit light signals for data, unrelated to ultrasound.
• D: Sunbeds emit UV light for tanning, not involving sound frequencies.

Final answer: A