Electromagnetic radiation energy units

Section 13 20 IR spectroscopy probes molecular structure by examining transitions between vibrational energy levels using electromagnetic radiation m the 625-4000 cm range The presence or absence of a peak at a charac tenstic frequency tells us whether a certain functional group is present Table 13 4 lists IR absorption frequencies for common structural units... 

An explanation of the many units used to describe the energy of electromagnetic radiation is provided in the following paper. 

I is defined as the energy / unit area of a beam of electromagnetic radiation. 

Net Ionic Equation a chemical equation that shows only the ionic species that actually take part in the reaction Neutralization process that occurs when an acid reacts with a base, a type of reaction involving an acid and base Newton SI unit for force equal to 1 kg-m/s Nonelectrolyte a substance that does not conduct current when it is dissolved in water Nonionizing Radiation electromagnetic radiation with insufficient energy to dislodge electrons and cause ionization in human tissue, for example, radio waves, microwave, visible light Nonmetal elements found on the right side of the periodic table that conduct heat and electricity poorly... 

Table 1.1 Equivalence oiirequency. wavelength and energy units for electromagnetic radiation...

A simple thought experiment due to Einstein gives a basic idea of the interaction of electromagnetic radiation with matter. Consider a space surrounded on all sides by perfectly reflecting mirrors (Figure 2.9). Inside this cavity there is a hot material body which is in thermal equilibrium with the radiation which fills the cavity. This radiation is then isotropic, as it fills, in a random manner, all the space of the cavity its intensity can be defined as an energy per unit volume. 

Figure 9-7 The span of the spectrum of electromagnetic radiation used in spectroscopic investigations of organic compounds along with comparison of some of the various units commonly employed for wavelength and energy of the radiation on log scales...

In optical experiments the absorption of radiation is governed by the Beer-Lambert law. If I0(E) is the measured intensity of a beam of electromagnetic radiation of energy E and 1(E) that following absorption by a gas of thickness L containing n molecules per unit volume, then 21... 

The proportionality constant h has the dimensions of energy times time and has the value of 6.62 x 10 27 erg-sec. It is called Planck s constant and is the same for all types of electromagnetic radiation. Since energy seems to come in discrete units, this quantization thus permits us to view radiation also in terms of particles, the photons. Absorption of photons by atoms would increase their energy by an amount equivalent to hv per photon. 

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