The electric potential on the boundary of a spherical cavity of radius R, as a function of the polar angle θ, is \(V_0 \cos ^2 \frac{\theta}{2}\). The charge density inside the cavity is zero everywhere. The potential at a distance R/2 from the centre of the sphere is
1
\(\frac{1}{2} V_0\left(1+\frac{1}{2} \cos \theta\right)\)
2
\(\frac{1}{2} V_0 \cos \theta\)
3
\(\frac{1}{2} V_0\left(1+\frac{1}{2} \sin \theta\right)\)
4
\(\frac{1}{2} V_0 \sin \theta\)