JEE Main 202621 JanuaryEvening Shift
- Exam
- JEE Main
- Year
- 2026
- Date
- 21 January
- Shift
- Evening Shift
- Subject
- Physics
- Chapter
- Mechanical Properties of Fluids
JEE Main 2026 · 21 January · Evening Shift · Physics · Mechanical Properties of Fluids
Surface tension of two liquids (having same densities), T_ 1 and T_...
Surface tension of two liquids (having same densities), and , are measured using capillary rise method utilizing two tubes with inner radii of and where . The measured liquid heights in these tubes are and respectively. [Ignore the weight of the liquid about the lowest point of miniscus]. The heights and and surfaces tensions and satisfy the relation:
Options
- A
- B
- C
- D
Correct answer
D.
Step-by-step solution
For capillary rise, the height of liquid in a tube is given by: , where is surface tension and is the tube radius.
For two liquids with equal density and contact angles:
and
Taking the ratio:
Since , we have . The capillary rise is inversely proportional to tube radius, so the smaller radius tube will have greater height. Since the liquids are measured to have heights and with , and they have the same density, the empirical relation shows that both liquids rise to different heights inversely proportional to their radii. For liquids with the same density measured in different tubes, if the heights and radii satisfy the capillary rise equation, the surface tensions must be equal: , and since .
For two liquids with equal density and contact angles:
and
Taking the ratio:
Since , we have . The capillary rise is inversely proportional to tube radius, so the smaller radius tube will have greater height. Since the liquids are measured to have heights and with , and they have the same density, the empirical relation shows that both liquids rise to different heights inversely proportional to their radii. For liquids with the same density measured in different tubes, if the heights and radii satisfy the capillary rise equation, the surface tensions must be equal: , and since .