Multiple choice

Which one of the following statements concerning a vacuum flask is correct?

  1. The silvering makes the surface a poor conductor

  2. The vacuum reduces the loss of heat by radiation

  3. It can only be used to keep things warm

  4. The silvered surface reduces loss of heat by radiation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The silvered surfaces inside a vacuum flask act as mirrors for infrared radiation. They reflect heat back toward the contents (if hot) or away from them (if cold), significantly reducing heat transfer by radiation.

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