Indirect illumination may be provided by floodlights, spotlights, ordinary incandescent bulbs, fluorescent tubes or mercury-vapor lamps. Internally illuminated signs shall be permitted only for commercial and industrial uses. Regardless of the type of illumination employed, all illuminated signs, and/or the light fixtures illuminating the signs, shall be properly shielded and so located as to prevent glare or blinding effects upon surrounding buildings, properties, or motor vehicle traffic so as not to cause a nuisance or hazard to building occupants, residents or travelers in the area.