Surface Tension

Consider a uniform sphere of radius R and mass M. A spherical cavity of radius R/2 is made in the sphere as shown in figure. The magnitude of the gravitational intensity at a point O on the surface of the cavity is

Two media A and B are separated by a plane boundary surface. The speed of light in medium A and B are 2 x 10⁸ m/s and 2.5 x 10⁸ m/s respectively. The critical angle for which a ray of light going from A to B will have total internal reflection is A

As shown above, a hollow cylinder has a charge q within it. If Φ is the electric flux through the curved surface ‘B’, then the flux linked with the plane surface ‘A’ is,