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Question
Assertion A: Sharp glass edge becomes smooth on heating it upto its melting point.
Reason R: The viscosity of glass decreases on melting.
Choose the most appropriate answer from the options given below.
Options
Both A and R are true and R is the correct explanation of A.
A is true but R is false.
A is false but R is true.
Both A and R are true but R is NOT the correct explanation of A.
Solution
Both A and R are true but R is NOT the correct explanation of A.
Explanation:
Sharp glass edges become smooth when heated until they reach their melting point. This is referred to as glass fire polishing. Fire polishing is a technique used in glass fabrication. During this process, on cutting a glass tube or a rod, the surface left behind edge which is rough and sharp. When heat is applied to a rough or sharp edge, it becomes smooth, polishing the edge to a smooth surface. When glass melts, surface tension causes the previously rough and pointy edge to become smooth.
