Final answer:
The wavenumber, reported in cm^-1, is inversely proportional to the wavelength and directly relates to the frequency and energy of a light wave. It is commonly used in spectroscopy to describe the number of wave cycles per centimeter.
Step-by-step explanation:
The quantity that is inversely proportional to the wavelength and reported in reciprocal centimeters (cm-1) is known as the wavenumber. In the context of spectroscopy, wavenumbers provide a way to express frequencies of light waves. According to the relationship highlighted by Planck's formula, E = hu, where E is energy, h is Planck's constant, and u is frequency, it is evident that frequency is directly proportional to energy, while wavelength is inversely proportional. Consequently, as frequency increases, the wavelength shortens, resulting in a higher wavenumber.
In spectroscopy, various sections of the electromagnetic spectrum are often discussed in units that are most convenient for the wavelength or frequency range in question. For example, radio waves may be expressed in megahertz (MHz), while visible light is often stated in nanometers (nm) or Angstroms. Infrared spectrums, visible light, and ultraviolet light have their unique ranges expressed in cm-1, which are customarily used to describe the number of wave cycles in one centimeter of distance, thus correlating directly to energy levels of the photons.