Liquid rises to a height of 2 cm in a capillary tube and the angle of contact between the solid and the liquid is zero. If the tube is depressed more now so that top of capillary is only 1 cm above the liquid, then the apparent angle of contact between the solid and the liquid is

Options

A. `30^(@)`
B. `60^(@)`
C. `0^(@)`
D. `90^(@)`

Answer

B

Explanation

In the first case, `T = ( rhrhog)/(2 cos theta) `
` :. Cos theta = (r rho g.(2))/(2T) ` where h = 2
` :. Cos 0^(@) = 1 = (r rhog)/T " " :. T = rrho g `
In the second case , h = 1 , so `theta ` will change , then
` cos theta ' = (r rho g(1))/(2T) = h = 1 cm and T = r rho g `
` = (rrhog)/(2.rrhog) =1/2`
` :. ". theta' = 60^(@)`