seen from the Gauss's law, considering that the dipole field decreases at the cube of the distance at large distances, and the therefore total flux of the field though an infinitely large sphere vanishes. Because electric fields satisfy the superposition principle, a conducting plane below multiple point charges can be replaced by the mirror images of each of the charges individually, with no other modifications necessary. Electric dipole moments The image of an electric dipole moment p at above an infinite grounded conducting plane in the xy-plane is a dipole moment at with equal magnitude and direction rotated azimuthally by π. That is, a dipole moment with Cartesian components will have in image dipole moment . The dipole experiences a force in the z direction, given by and a torque in the plane perpendicular to the dipole and the conducting plane, Reflection in a dielectric planar interface Similar to the conducting plane, the case of a planar interface between two different dielectric media can be considered. If a point charge is placed in the dielectric that has the dielectric constant , then the interface (with the dielectric that has the dielectric constant ) will develop a bound polarization charge. It can be shown that the resulting electric field inside the dielectric containing the particle is modified in a way that can be described by an image charge inside the other dielectric. Inside the other dielectric, however, the image charge is not present. Unlike the case of the metal, the image charge is not exactly opposite to the real charge: . It may even have the same sign, if the charge is placed inside the stronger dielectric material (charges are repelled away from regions of lower dielectric constant). This can be seen from the formula. Reflection in a conducting sphere Point charges The method of images may be applied to a sphere as well. In fact, the case of image charges in a plane is a special case of the case of images for a sphere. Referring to the figure, we wish to find the potential inside a grounded sphere of radius R, centered at the origin, due to a point charge inside the sphere at position (For the opposite case, the potential outside a sphere due to a charge outside the sphere, the method is applied in a similar way). In the figure, this is represented by the green point.