JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Solid State

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Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R.
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.

(A) $A$ is false but $R$ is true.
(B)Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$ .✓ Correct
(C) $A$ is true but $R$ is false
(D)Both $A$ and $R$ are true and $R$ is the correct explanation of $A$ .

Answer: (B)

Solution

Assertion A is true: when glass is heated to its melting point, sharp edges become smooth due to surface tension effects and flow of the material. Reason R is also true: the viscosity of glass decreases significantly upon heating/melting, allowing it to flow. Furthermore, R correctly explains A — the decrease in viscosity allows the glass to flow and redistribute, smoothing out sharp edges due to surface tension minimization. The correct answer is (D).

JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Single correct option

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JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Solid State

Solution

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