Echo sounder and incandescent light bulb: what they have in common

1. Step 1. Echo sounder — has part — Hydrophone. A hydrophone listens for the echo.
2. Step 2. Hydrophone — uses — Piezoelectric effect. A piezo element.
3. Step 3. Piezoelectric effect — is used in — Lighter. Piezo lighters.
4. Step 4. Lighter — has part — Wick. Petrol lighters have a wick.
5. Step 5. Wick — is part of — Oil lamp. The wick feeds oil to the flame.
6. Step 6. Oil lamp — evolved into — Incandescent light bulb. The electric lamp replaced oil and gas lamps.

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