Correct Option
Assertion (A) states that when a piece of copper and a piece of glass are heated to the same temperature, the copper piece appears hotter when touched. This assertion is true. Copper is a good conductor of heat, possessing high thermal conductivity. When touched, it rapidly transfers heat to the skin, causing a more intense sensation of heat compared to glass, which is a poor conductor of heat (low thermal conductivity).
Reason (R) states that the density of copper is more than that of glass. This reason is factually true. The density of copper is approximately 8.96 g/cm³, while the density of common glass is around 2.5 g/cm³ to 2.8 g/cm³.
However, Reason (R) is not the correct explanation for Assertion (A). The perceived difference in temperature when touching objects at the same actual temperature is primarily due to their thermal conductivity, not their density. Objects with higher thermal conductivity transfer heat to or from the skin more quickly, leading to a stronger sensation of heat or cold. Therefore, both A and R are true, but R does not explain A.
Incorrect Options
Option 1 is incorrect because while both A and R are true, R (density difference) is not the correct explanation for A (perceived temperature difference due to thermal conductivity).
Option 3 is incorrect because Reason (R) is factually true; copper is indeed denser than glass.
Option 4 is incorrect because Assertion (A) is true. The phenomenon described, where a good conductor feels hotter or colder than a poor conductor at the same temperature, is a well-established concept related to thermal conductivity.