1. The problem statement, all variables and given/known data Given a dielectric sphere with relative permittivity = ε in a homogeneous E-field: [itex]\vec{E_{0}} = E \vec{e_{z}}[/itex]. The E-field causes a homogeneous polarisation (dipole density) of [itex]\vec{p} = \frac{vec{P}}{V} [/itex] with big P the dipole moment vector. The total electric field outside is: [itex]\vec{E^{ex}} = \vec{E_{0} - \frac{1}{4 \pi \epsilon_{0}} ( \frac{\vec{P}{r^{3}} - \frac{\vec{3P}{r^{5}}} ) [/itex] Question: Use the continuous nature of the normal component of [itex]\vec{D}[/itex] at the surface to show that: [itex]\epsilon_{0} E^{in} = E_{0} + \frac{2P}{4\pi\epsilon_{0}}[/itex] 2. Relevant equations Using [itex]\vec{D^{ex}_{n}} = \vec{D^{in}_{n}}[/itex] , e.g. normal component of D is continuous at surface and [itex]\vec{\frac{D^{ex}_{t}}{\epsilon_{0}}} = \vec{D^{in}_{t}}[/itex] 3. The attempt at a solution I simply don't know what to do I've messed around with this and got nowhere. Please help! Latex isn't rendering properly - vector arrows are appearing as small boxes but please try and help!!