Question

why do people blow air on their spectacles before cleaning them​

Answer 1

As a result, the water vapours present in the air surrounding the glass condense and get attached to the glass surface. ⚫hence the glass can be wiped properly due to presence of water droplets. ⚫so , people blow air into their spectacles before cleaning them.

Answer 2

If we blow air on the spectacles it gets moist .so that we clean it soon and smooth