Absorbance is the measure that indicates the attenuation of radiation when passing through an element.
The concept of absorbance is used in the field of physics . This is the measurement that reflects how radiation is attenuated when it passes through an element . Absorbance can be expressed by a logarithm that arises from the link between the intensity leaving and the intensity entering the substance.
Also referred to as absorbency (the act of absorbing: attracting something to incorporate or consume it), absorbance depends on the concentration and thickness of the sample. This proportional relationship differentiates this measurement from transmittance , whose magnitude reflects the amount of energy that passes through an element in a certain unit of time.
Types of transmission
The breadth of the concept of transmittance means that we can distinguish two types: thermal and optical transmittance. The first is the one set out in the previous paragraph and it can be added that the element that the energy passes through is called constructive , since it is part of a construction work, and its faces must be parallel to each other.
Optical transmittance can be defined as the portion of the incident light that manages to pass through a sample , maintaining a certain wavelength, and is expressed by the equation light intensity of the sample over intensity of the incident ray . Normally the result is presented as a percentage.
Once the light passes through a sample, the value equivalent to its intensity is obtained, and for this it is essential to know its wavelength, that is, the real distance that a wave travels in a given time interval. Said segment in time is the one that takes place between two maximum points of some of the physical properties of the wave, and they must occur consecutively.
For electromagnetic waves , said physical property could be the electrical effect: as the wave moves forward, it approaches a maximum, then decreases until nullification, acquires a negative value and reaches its minimum (a concept that we can also call maximum negative ). As expected, this process is repeated indefinitely, which is why it also occurs in the opposite direction until another positive maximum is reached.
Absorbance can be linked to optical density.
Absorbance and optical density
When absorbance is calculated per unit length, on the other hand, the idea of optical density is used. This physical quantity specifically refers to the level that an optical element absorbs according to the unit of distance, taking into account a specific wavelength.
Other points discussed in this definition also come into play in the concept of optical density: in addition to the distance traveled by light in a given sample, that is, its thickness , which is measured in centimeters, we must take into account the absorbance value , the transmittance and the intensity of each ray of light, both the one that hits and the one that is transmitted. As a reference, there must be an inverse proportion between optical density and transmittance : the higher the first, the shorter the second.
The concept and spectrophotometry
Spectrophotometry indicates that absorbance is calculated by dividing the intensity of the light that passed through a sample by the intensity of the light that existed before entering said sample. In other words: the intensity that comes out or is transmitted is related to the intensity that enters or incident.
Absorbance, in short, quantifies the phenomenon that occurs with light radiation and substances. When light falls on the sample, a part of the radiation is absorbed by the substance. The light that is not absorbed passes through the sample: when it is captured by a receiver located on the other side, it is possible to carry out the measurement.