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garlopf t1_ja5tqgd wrote

You can block sound completely by isolating the source of the sound from the ear with vacuum. As sound is waves traveling through matter, it can only travel where there is matter.

Light on the other hand is electro magnetic waves, which will travel wherever there is an electro magnetic field, including in vacuum. Light will interact with matter and you can block light completely by enclosing it in reflective and/or bsorbent material.