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.

पर्याय

• 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.

Answer 1

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.