Assertion (A): A narrow glass tube when immersed into mercurycauses ca...
Assertion (A): A narrow glass tube when immersed into mercury causes capillary depression, and when immersed into water causes capillary rise.
Reason (R): Mercury is denser than water.
Explanation:
When a narrow glass tube is immersed in a liquid, the liquid rises or falls inside the tube due to capillary action. Capillary action occurs due to the combination of adhesive and cohesive forces.
Capillary Depression:
When a narrow glass tube is immersed in mercury, the liquid inside the tube depresses or moves downward. This happens because the adhesive forces between the glass and mercury are stronger than the cohesive forces within the mercury. As a result, the mercury is pulled down into the tube, causing capillary depression.
Capillary Rise:
When the same glass tube is immersed in water, the liquid inside the tube rises. This occurs because the adhesive forces between the glass and water are weaker than the cohesive forces within the water. As a result, the water is pulled up into the tube, causing capillary rise.
Density Comparison:
The reason for the capillary depression in mercury and capillary rise in water is related to the density of the liquids. The density of mercury is much higher than that of water. Since the adhesive forces are stronger in mercury, it can overcome the gravitational force and pull the liquid down into the tube.
Explanation of Assertion and Reason:
Both the assertion and reason are individually true. The assertion correctly states the phenomena of capillary depression in mercury and capillary rise in water. The reason correctly explains the cause behind these phenomena, which is the difference in density between mercury and water.
The adhesive and cohesive forces play a crucial role in determining the direction of capillary action. The difference in density between the liquid and the tube material affects the balance between these forces, leading to either capillary depression or capillary rise.
Conclusion:
In conclusion, both the assertion and reason are true, and the reason is the correct explanation of the assertion. The density difference between mercury and water determines the direction of capillary action in a narrow glass tube.