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asdf1
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if frequency is (1/sec), then why is wavenumber (1/cm) considered a unit of frequency?
It is considered the spatial representation of frequency, it in itself is not a fequency. However, you can obtain the the wavenumber by dividing the frequency by the speed of light. Observe,asdf1 said:if frequency is (1/sec), then why is wavenumber (1/cm) considered a unit of frequency?
Frequency refers to the number of occurrences of a repeating event per unit time. It is typically measured in hertz (Hz). Wavenumbers, on the other hand, refer to the number of waves that pass a fixed point per unit distance. They are usually measured in units of inverse meters (m^-1). Frequency and wavenumbers are mathematically related through the formula: wavenumber = frequency * speed of light.
In spectroscopy, frequency and wavenumbers are used to measure the energy of a particular electromagnetic wave. This is because the energy of a wave is directly proportional to its frequency and inversely proportional to its wavelength (which is related to wavenumbers). Spectroscopy techniques use this relationship to identify and analyze the chemical composition of substances based on the unique energy signatures of their molecular vibrations or electronic transitions.
Infrared (IR) and Raman spectroscopy are both techniques used in spectroscopy to analyze the vibrational energy levels of molecules. The main difference between the two is that IR spectroscopy measures the absorption of infrared light by a molecule, while Raman spectroscopy measures the scattering of light. In terms of frequency and wavenumbers, IR spectroscopy typically uses higher frequencies and wavenumbers (4000-400 cm^-1) compared to Raman spectroscopy (400-10 cm^-1).
In NMR spectroscopy, frequency and wavenumbers are used to measure the energy differences between the different spin states of atomic nuclei in a magnetic field. This allows for the identification and characterization of molecules based on their unique NMR spectra. The frequency of the radio waves used in NMR spectroscopy is typically in the range of 10-1000 MHz, which corresponds to wavenumbers of 1-100 m^-1.
In spectroscopy, frequency and energy are directly proportional. This means that the higher the frequency of a wave, the higher its energy and vice versa. This relationship is described by the equation: energy = Planck's constant * frequency. This is why spectroscopy techniques, such as IR and NMR, use the frequency/wavenumber measures to determine the energy levels of molecules and identify their chemical composition.