Water rises to a height of `10 cm` in a capillary tube and mercury falls to a depth of 3.42 cm in the same capillary tube. If the contact angle for me
Water rises to a height of `10 cm` in a capillary tube and mercury falls to a depth of 3.42 cm in the same capillary tube. If the contact angle for mercury and surface tension of water and mercury is
A. `1:0.15`
B. `1:3`
C. `1:6.5`
D. `1.5 : 1`
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Correct Answer - C
As, height raised `h=(2S cos theta)/(r rho g)`
or `S=(hr rho g)/(2 cos theta) implies S prop (h rho)/(cos theta)`
`:. S_(w)/S_(Hg)=h_(1)/h_(2)xx(cos theta_(2))/(cos theta_(1))xxrho_(1)/rho_(2)`
`=10/((-3.42))xx(cos 135^(@))/(cos 0^(@))xx1/13.6`
`S_(w)/S_(Hg)=10/3.42xx0.707/13.6=1/6.5`
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