 Hz or s-1) is defined as (n) = P/(hv), where h = 6.62 X 10-34 J/s is Planck's constant. 25.8 Electromagnetic waves, polarization states, photons, and quantum measurements E (t) direction M (t) Figure 25.2 Electromagnetic wave associated with a light ray, showing electric (E) and magnetic (M) components oscillating in orthogonal planes made up of two oscillating field components, one electrical (E) and one magnetic (M), as illustrated in Fig. 25.2. The two EM field components oscillate in planes orthogonal to the direction of the EM-wave propagation, which is that of the associated light ray. The direction pointed to by either the E-field or the M-field oscillation is referred to as light polarization. When the E-field direction is orthogonal to the ray direction, one refers to the light beam as being transverse-electric, or TE-polarized. In the other case, where the M-field is orthogonal to the ray, the light is called transverse-magnetic, or TM-polarized. When the polarization is either TE or TM, light is said to be linearly polarized. For short, we can say that linearly polarized light is either vertically (TE) or horizontally (TM) polarized. As a first hint of quantum mechanics, one refers to the TE and TM possibilities as polarization states. Consistently, the TE and TM polarization states are said to be orthogonal. Occasionally, I shall designate the TE and TM states by the symbols and <>, respectively. Linear polarization, in fact, represents a special case where the E-field component oscillates with a constant direction in space, meaning that its oscillation plane is fixed. In the most general case, we may conceive of the E-field as resulting from the superposition of two orthogonally polarized components E1, E2, each one being characterized by its own phase, Q1,Q2. If the two components are in phase (61 = Q2), then the resulting E-field is linearly polarized. If not (61 # 42), the resulting E-field direction rotates over time. To see this more clearly, define an orthonormal basis 1, associated with the t