An electrodeless plasma lamp having a lamp body and a power source configured to provide radio-frequency (RF) power via a feed to the lamp body is provided. The lamp includes a first conductive element and a second conductive element. The first conductive element has a first side with a first protrusion. The second conductive element has a second side with a second protrusion. The first side and second side face each other and spaced apart by a first distance and configured to couple the RF power via an electric field to a fill to form at least one plasma arc. The first protrusion and the second protrusion extend towards each other and are spaced apart by a second distance that is less than the first distance. The first and second protrusions may provide localized enhancement of the electric field at the first side and the second side.