Superposition rules when it comes to calculating the light emanating from a two-slit screen. This example is a computer simulation:
| Monochromatic light | Three colors |
|---|---|
|
|
Electric fields may be visualized in terms of vectors, displayed at various points around a charge distribution (WP, Ch. 23), or in terms of field lines (WP, Ch. 24). Below are images which depict both representations for several different charge distributions.
| Monopole (single point charge) | Dipole | Quadrupole |
|---|---|---|
|
|
|
In the presence of conductors, electric fields get distorted (in a sense) so that the field is perpendicular to a conductor's surface. Here we see a flat conducting slab extending from about x=0.2 into negative-x values. Note how the electric field vectors are perpendicular to the vertical line at the surface of the conductor. On the surface, charges distribute themselves so as to maintain this configuration; positive charges are green points, negative charges are in red. (Please click on the images to see the figures in full resolution.)
The electric potential is not a vector, but is instead analogous to elevation (proprotional to the gravitational potential) of points on the surface of the earth. Topological maps often show lines of constant elevation (contours), and we may similarly map "equipotential" contours -- lines of constant electric potential. Here are some examples showing equipotential lines along with field lines and electric field vectors (here the field lines are colored magenta while the equipotential surfaces are green (for V>0) and red (V<0)). The left image is for a point charge, the right image is a dipole.
Next we plot equipotentials in the presence of a conductor (see above). For this image the color map is slightly different -- cyan is positive potential, magenta is negative. The surface charges are shown in green and red as above.
Finally, to emphasize the analogy with topological maps, here is an "elevation map" showing potential as a height above or below the x-y plane. The equipotential contours are plotted on the left. (The color map is returned to the field lines being magenta, equipotentials are red/green.)
