Radio Waves

Radio waves are perhaps the most familiar portion of the electromagnetic spectrum. This radiation has long wavelength, low frequency, and low energy. By themselves, radio waves have little direct effect on matter. Chemists and physicists however have devised a way to make use of radio waves to help elucidate the structures of molecules.

In nuclear magnetic resonance (NMR) spectroscopy, a compound is placed between the poles of a strong magnet and irradiated with radio waves. Some of the radiofrequency energy is absorbed and the resulting spectrum obtained is then correlated with the structure of the molecule.

A simplified diagram of an NMR spectrometer.

Magnetic resonance imaging (MRI) is an offshoot of NMR that is used in the medical field to obtain images of tissues. MRI is useful in imaging soft tissues such as brains and hearts and thus complements medical X-rays which are more useful at imaging hard tissue such as bone. The reason that the term MRI was invented for medical applications of NMR rather than using the term NMR itself was that members of the scientific community felt that if the term contained the word "nuclear", patients would associate negative connotations with the diagnostic procedure and would thus be reluctant to have the procedure done.

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