A liquid of density `rho` and surface tension `sigma` rises in a capillary tube of inner raduis R. The angle of contact between the liquid and the glass is `theta`. The point A lies just below the maniscus in the tube and the point B lies at the outside level of liquid in the beaker as shown in figure. The pressure at A is

Options

A. `p_(B)-rhogh`
B. `p_(B)-(2 sigma cos theta)/(R )`
C. `p_(atm)-(2 sigma cos theta)/(R )`
D. All of these

Answer

D

Explanation

Radius of meniscus `=(R )/(cos theta)=r`
`Delta p` due to sperical surface`=(2 sigma)/(r)`
`=(2 sigma cos theta)/(R )`
`p_(B)=p_(atm)`.