Answer :
The angle of contact between a liquid and the container is an important concept in the study of surface tension and capillarity. This angle is defined at the point where three phases meet: the liquid phase, the solid phase (container), and the gas phase (usually air).
Here's a detailed explanation:
(A) Length of the liquid surface: The length of the liquid surface is not about an angle but rather a linear measurement. It's not a characteristic related to the angle formed at any point of contact.
(B) Meniscus of the liquid surface: The meniscus of the liquid surface is relevant to the angle of contact. It is the curve seen at the top of a liquid in response to its container. At the edge where the liquid meets the container, a concave or convex meniscus forms, depending on the adhesive and cohesive forces between the liquid and the container. This contact point is where the angle of contact is measured.
(C) Size of the solid: The size of the solid (container) is not directly related to the angle of contact. Regardless of the size, the angle of contact is determined by the interaction between the liquid and the specific material of the solid.
(D) Depth of the liquid in the container: The depth of liquid is a vertical measurement from the liquid's surface down to the bottom of the container. It is unrelated to the interaction at the contact point that defines the angle of contact.
Considering these explanations, the correct answer is:
(B) Meniscus of the liquid surface
Because the angle of contact is specifically related to the point where the liquid's surface meets the container's wall, and that is represented by the meniscus.
