The speed of sound will be fastest in _____.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Iron bar
Sound is a mechanical wave: it is passed on by the particles of a medium pushing their neighbours. The particles of a solid are tightly bound, so a solid passes the push on fastest; sound travels fastest in solids, slower in liquids and slowest in gases. In iron its speed is about 5,000 m/s or more.
Why the other options are incorrect
Option (2) Water — Incorrect. Water is a liquid; sound moves through it at about 1,500 m/s.
Option (3) Hill top — Incorrect. At a hill top sound travels through air, a gas, at about 330–340 m/s, a little less where the air is colder.
Option (4) Vacuum — Incorrect. A vacuum has no particles to carry the wave, so sound cannot travel through it at all.