Metallic Delay Lenses

AN experimental study of the metallic delay lens described by Kock1 has been made in this Establishment, using a lens constructed of parallel strips as in Fig. 1, the E vector being normal to the line of the strips. The dimensions were such that Kock's formula for refractive index where s is width of strips and N is number of strips per unit area viewed end on, gave the value 1.41 for n. The predicted cut-off wave-length was 1.8 cm.