Two liquids A and B have θ A and θ B as contact angles in a capillary tube. If K=frac cos θ A cos θ B , then identify the correct statement:

K is negative, then liquid A has concave meniscus and liquid B has convex meniscus.

K is zero, then liquid A has convex meniscus and liquid B has concave meniscus.

K is negative, then liquid A and B have convex meniscus.

K is negative, then liquid A and liquid B have concave meniscus.

Physics · Mechanical Properties of Matter

JEE Main 2025 — 4 April, Morning Shift — Question 61

Two liquids $A$ and $B$ have $\theta_{A}$ and $\theta_{B}$ as contact angles in a capillary tube.

If $K=\frac{\cos \theta_{A}}{\cos \theta_{B}}$ , then identify the correct statement:

Option A:
$K$ is negative, then liquid $A$ has concave meniscus and liquid $B$ has convex meniscus.
Correct
Option B:
$K$ is zero, then liquid $A$ has convex meniscus and liquid $B$ has concave meniscus.
Option C:
$K$ is negative, then liquid $A$ and $B$ have convex meniscus.
Option D:
$K$ is negative, then liquid $A$ and liquid $B$ have concave meniscus.

For concave meniscus $\theta_{A}<90^{\circ}$ For convex meniscus $\quad \theta_{B}>90^{\circ}$ $\frac{\cos \theta_{A}}{\cos \theta_{B}}<0$

Answer key and solution verified before publishing.

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