APPENDIX VI.
Reading edition
ELLIPTICALLY POLARISED ELECTRIC RADIATION.
Since the delivery of my lecture to the Royal Institution, on June 1st, Herr Zehnder has published[41] a mode of getting elliptically and circularly polarised electric radiation. He takes a couple of plane polarising grids, such as are depicted in Fig. 21, page 37, and places them parallel to each other at a little distance apart with their wires crossed.
If the two grids are close together they will act like wire-gauze, reflecting any kind of polarised radiation equally; but if the warp and woof are an eighth-wave length apart, and the plane of the incident radiation is at 45° to the wires, the reflected radiation will be circularly polarised. A change in the circumstances will, of course, make it elliptical. Such a pair of grids acts, in fact, like a Babinet’s Compensator.