List of Contents
Monochromatic light is electro-magnetic radiation containing one color. In physical terms it represents radiation with one angular frequency (w). The propagation direction of light is indicated by a vector, which is called the k vector. Monochromatic light is completely polarized (this is generally true if the light is strictly monochromatic, but not generally so if there is a finite band width). This means that the electric radiation field describes, as a function of time, a circle, a line, or an ellipse at a fixed position in space (Figure (a)). Accordingly, light is called circularly, linearly, or elliptically polarized. The magnetic field executes an accompanying motion, which is dictated by Maxwell’s equations. With each form of polarized light, there is a complementary form of polarization. The complement is obtained by (1) rotation over 90° and (2) reversal of the motion. The couples thus obtained have orthogonal polarization. Orthogonal couples have either left and right circular polarization, left and right elliptical polarization, or parallel and perpendicular polarization (with respect to a spatial axis). Each orthogonal couple forms a mathematical basis in which any form of polarized radiation can be expressed by linear combination (Figure (b)).
By definition, clockwise rotation is called right and anti clockwise rotation left (see Footnote). Right circularly polarized light is light of which the electric and magnetic field components rotate to the right (= clockwise) for an observed who looks into the beam (that is, an observer who looks to the source, in a direction opposite to the k vector). Left circularly polarized light is light of which the electric and magnetic field components rotate to the left (= anti clockwise) for an observer who looks into the beam.
Footnote: We have adopted the chemical convention for right and left polarization. This convention is opposite to that used in the physical literature. Of course, the physicist’s convention is more appropriate as the thumb of the left (right) hand indicates the propagation direction of the light of which the physical left (right) rotational sense is given by the fingers (Figure c, d)). Our choice (i.e., chemists’ convention) was made to be consistent with the extensive chemical literature on optical activity.
List of Contents