Two liquids A and B have contact angles $\theta_{A}$ and $\theta_{B}$ in a capillary tube. If K = cos $\theta_{A}$ /cos $\theta_{B}$ , identify the correct statement.
Options

Question

Two liquids A and B have contact angles $\theta_{A}$ and $\theta_{B}$ in a capillary tube. If K = cos $\theta_{A}$ /cos $\theta_{B}$ , identify the correct statement.

Options

G1 Physics · Accepted Answer

For a liquid in a capillary tube: • θ < 90° ⇒ cosθ > 0 ⇒ concave meniscus. • θ > 90° ⇒ cosθ < 0 ⇒ convex meniscus. Given K = cosθA/cosθB. If K < 0, cosθA and cosθB have opposite signs. Hence one contact angle is acute and the other is obtuse, so one meniscus is concave and the other is convex. The source paper marks option C. Strictly, the condition K < 0 by itself fixes only that the two menisci are of opposite type; it does not uniquely identify which liquid is concave witho…

Two liquids A and B have contact angles θ A \theta_{A} θ A ​ and θ B \theta_{B} θ B ​ in a capillary tube. If K = cos θ A \theta_{A} θ A ​ /cos θ B \theta_{B} θ B ​ , identify the correct statement.

Two liquids A and B have contact angles θ A \theta_{A} θ A and θ B \theta_{B} θ B in a capillary tube. If K = cos θ A \theta_{A} θ A /cos θ B \theta_{B} θ B , identify the correct statement.