A capillary glass tube records a rise of 20 cm when dipped in water. When the area of cross-section of the tube is reduced to half of the former value, water will rise to a height of:
If cross section
area is reduced to half, then radius of capillary tube becomes
1√2 times of the previous one. i.e
r′=r√2
The height h through which a liquid
will rise in a capillary tube of radius r is given by h=2Scosθrρg
where S is the surface
tension, ρ is the density of the liquid and θ is the
angle of contact.
We see that h∝1r, So we
have
h′h=rr′
⇒h′h=√2⇒h′=√2h=√2×20=20√2cm