Luminous Intensity Distribution
Using “field diagrams” is an easy way to determine whether the lamp has a “narrow” or “wide” beam of light. They also show whether the light beam is symmetrical or not. The diagram in the figure below shows that the maximum intensity of light (yellow area) is just below the lamp (0 °). The light intensity decreases with the increase of the angle of illumination and virtually disappears after crossing the angle of 15 ° (vertical lines in the diagram). The light intensity on the right and left of the line 0 ° are almost identical, which shows that the beam is symmetrical.