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Question
Have you seen someone blowing on their spectacles to wipe them clean? How does the air from the mouth help in cleaning the spectacles?
Solution
The air blown from the mouth is hot and the glass of the spectacles is comparatively colder. The hot air we breathe out contains water vapours which turn into tiny droplets of water when it comes in contact with the colder glass. This makes the glass moist and hazy.
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