16
H. Rott
+-- Frequency f [Hz]
I
I
I i i
I
I i i
I
10 17 10 16 10 15 10 14 10 13 10 12 10 11 10 10 10 9 10 8
Wavelength A [m]--+
1~1~1~1~1~1~1if1~ 1if
uv
Infrared
f [GHz] 300 100
30
10
3
1
0.3
Fig. 2.1. Frequency, wavelength, and nomenclature of the electromagnetic spectrum from the ultraviolet (UV) to the microwave region
Wavelength, A, and frequency, v, are related by the equation A = cjv
where c is the velocity of the wave. The electromagnetic waves are characterized by A (or v), the direction of propagation, the amplitude, A, and the
polarization (Fig. 2.2). The electric field vector is used to define the direction
of wave polarization. In remote sensing, the surface upon which the wave is
incident is usually taken as the reference plane. A wave is horizontally polarized if the electric field vibrates in a plane which is parallel to the surface, and
vertically polarized if it vibrates perpendicular to that plane. Solar radiation
and thermal emission are usually specified in terms of intensity, which within
an isotropic medium is proportional to the square of the amplitude of the
electrical field.
x
z
Fig. 2.2. The electric field component E of a plane electromagnetic wave, linearly
polarized in x-direction, propagating in z-direction