2.1 Electromagnetic Energy
Energy is a group of particles travelling through a certain media. Electromagnetic energy is a group of particles with different frequencies travelling at the same velocity. These particles have a dual-mode nature. They are particles but they travel in a wave form.
Electromagnetic waves obey the following rule:
This equation explains that the shorter wavelength has higher spectral frequency
Electromagnetic energy is a mixture of waves with different frequencies. It may be viewed as:
Each wave represents a group of particles with the same frequency. All together they have different frequencies and magnitudes.
With each wave, there is an electronic (E) component and a magnetic component (M). The Amplitude (A) reflects the level of the electromagnetic energy. It may also be considered as intensity or spectral irradiance. If we plot A against the wavelength l we then get an electromagnetic curve, or spectrum (Figure 2.1).
Figure 2.1. An electromagnetic spectrum
Any matter with a body temperature greater than 0 K emits electromagnetic energy. Therefore, it has a spectrum. Furthermore, different chemical elements have different spectra. They absorb and reflect spectral energy differently. Different elements are combined to form compounds. Each compound has a unique spectrum due to its unique molecular structure. This is the basis for the application of spectroscopy to identify chemical materials. It is also the basis for remote sensing in discriminating one matter from the other. Spectrum of a material is like the finger print of human being.