# Absorbance Dictionary Definitions

The concept of absorbance is used in the field of physics. This is the measurement that reflects how radiation attenuates when it passes through an element. Absorbance can be expressed by a logarithm that arises from the link between the intensity that leaves and the intensity that enters the substance.

Also referred to as absorbency (the act of absorbing: attracting something to incorporate or consume), absorbance depends on the concentration and thickness of the sample. This proportional relationship differentiates this measure of transmittance, the magnitude of which reflects the amount of energy that passes through an element in a certain unit of time.

The breadth of the concept of transmittance means that we can distinguish two types: thermal and optical transmittance. The first is the one exposed in the previous paragraph and it can be added that the element that passes through the energy is called constructive, since it is part of a construction site, and its faces must be parallel to each other.

Optical transmittance can be defined as the portion of incident light that can pass through a sample, maintaining a determined wavelength, and is expressed by means of 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 actual distance that a wave travels in a given time interval. This segment in time is the one that takes place between two maximum points of any of the physical properties of the wave, and they must occur consecutively.

For electromagnetic waves, this physical property could be the electrical effect: as the wave moves forward, it approaches a maximum, then decreases until cancellation, acquires a negative value and reaches its minimum (a concept that we can also call negative maximum). As expected, this process is repeated indefinitely, so it also occurs in the opposite direction until reaching another positive maximum.

When the absorbance is calculated per unit length, on the other hand, the idea of optical density is used. This physical magnitude specifically refers to the level that an optical element absorbs according to the distance unit, taking into account a determined wavelength.

Other points treated 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 intensity of each ray of light, both the one that falls and the one that is transmitted. For reference, there should be an inverse ratio between optical density and transmittance: the higher the former, the shorter the latter.

The spectrophotometry indicates the 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 goes 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. As light strikes the sample, some of the radiation is absorbed by the substance. Light that is not absorbed passes through the sample: when it is captured by a receiver on the other side, it is possible to carry out the measurement. 