Absorption Spectrum
Absorption Spectrum - Related Videos
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The Electromagnetic Spectrum
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The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the various colors of visible light has specific frequencies and wavelengths associated with them, and you can see that visible light makes up only a small portion of the electromagnetic spectrum. Because the technologies developed to work in various parts of the electromagnetic spectrum are different, for reasons of convenience and historical...
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The Electromagnetic Spectrum
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Electromagnetic waves are categorized according to their wavelengths and frequencies, giving the electromagnetic spectrum. These waves are classified as radio, infrared, ultraviolet, etc. Radio waves refer to electromagnetic radiation with wavelengths ranging from millimeters to kilometers. Radio waves are commonly used for audio communications (i.e., radios) and typically result from an alternating current in the wires of a broadcast antenna. They cover a broad wavelength range and are used...
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IR Spectrum
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When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber. Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
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The process of oral drug absorption can be influenced by several factors. Weakly acidic drugs tend to be absorbed more readily from the stomach due to their nonionized state. However, absorption may be less efficient in the upper intestine, where drugs are often ionized. Interestingly, despite the stomach's apparent advantage for drug absorption, its mucous layer can hinder diffusion. Its surface area is also smaller than the intestine's, which can further slow down the absorption rate. In...
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Executive Function in Autism Spectrum Disorder
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Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel—University of Southern California Attention, working-memory, planning, impulse control, inhibition, and mental flexibility are important components of human cognition that are often referred to as executive functions. Autism spectrum disorder is a developmental disorder that is characterized by impairments in social interaction, communication, and repetitive behaviors. It is a disorder that lasts a lifetime, and is thought to affect...
FAQs
A photon is absorbed only when its energy matches an allowed transition between quantized energy levels. The corresponding wavelength or frequency therefore marks a specific feature in the spectrum. Electronic transitions can produce absorption in one region, while vibrational and rotational transitions add molecular detail, allowing measurements to reflect both electronic structure and molecular motion.
Each substance has a particular arrangement of energy levels, so it absorbs a characteristic set of wavelengths or frequencies. That pattern reflects composition and electronic structure rather than simply the sample’s visual appearance. Comparing observed features with the substance’s characteristic pattern supports qualitative identification, especially when different compounds show distinguishable absorption behavior.
These transitions represent different forms of energy change within a substance. Electronic transitions involve electron energy levels, whereas vibrational and rotational transitions describe molecular motion. Because each transition type contributes features associated with different energy changes, an absorption spectrum can provide information about bonding, molecular structure, and electronic behavior rather than composition alone.
The Beer-Lambert law connects the measured absorption of radiation with the concentration of the absorbing substance, allowing an instrument signal to support quantitative analysis. A sample’s absorption features can therefore be used not only to recognize a compound but also to estimate how much is present. This makes spectroscopy useful for concentration measurements and reaction monitoring.
A sample is placed in the path of electromagnetic radiation, and an ultraviolet-visible or infrared spectrometer examines how the radiation changes across wavelengths or frequencies. Radiation matching allowed transitions is absorbed, while other portions pass through with little absorption. The instrument records the resulting pattern, which can then be interpreted for composition, structure, or concentration.
Qualitative analysis uses characteristic absorption features to help identify a substance, while quantitative analysis relates the measured absorption to concentration through the Beer-Lambert law. The same general measurement can therefore answer different questions depending on how the spectrum is interpreted. This flexibility supports compound identification, concentration determination, and monitoring changes during a reaction.
Repeated spectral measurements can track changing absorption features as a reaction proceeds, providing a way to monitor chemical transformation. The features also give clues about bonding and molecular structure because they arise from allowed electronic, vibrational, or rotational transitions. In this way, absorption measurements connect observed radiation behavior with chemical composition and molecular organization.