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UPCAT Science practice question 38: Which statement about a vacuum is correct?

Correct answer

B. Light travels through it, but sound cannot.

Sound is a mechanical wave and needs a material medium. Light is an electromagnetic wave and propagates through empty space.

Which statement about a vacuum is correct?

  1. Both sound and light travel through it.
  2. Light travels through it, but sound cannot.Correct
  3. Sound travels through it, but light cannot.
  4. Neither sound nor light can travel through it.

Why B is correct

Sound is a mechanical wave and needs a material medium. Light is an electromagnetic wave and propagates through empty space.

Why the other options are wrong

A Both sound and light travel through it.
Sound is a mechanical wave and needs particles to compress and rarefy, so it cannot cross a vacuum.
C Sound travels through it, but light cannot.
Reverses the two. Light is electromagnetic and needs no medium.
D Neither sound nor light can travel through it.
Would leave us unable to see the Sun, whose light crosses the vacuum of space.
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