Difference Between Absorbance and Transmittance

Main Difference

Absorbance and Transmittance are the two famous concepts that revolve around various fields like physics, analytical chemistry, quantitative and qualitative analysis, spectrometry and others. Both these terms can easily be differentiated as they are exactly opposite to each other. Following the Beer’s Law, it is known that when all the light hitting the surface of the object is absorbed then the transmittance is 0% and the absorption is 100%, on the other hand, if all the light hitting the surface of an object passes through the object then transmittance is 100% and absorption will be 0%. Both these values are mostly calculated in the percentage form as the absorbance gives the percentage in accordance with the light being absorbed with respect to the total intensity of light falling on the object, whereas transmittance gives the percentage in accordance with total light passing through the object surface with respect to the total intensity of light falling on object.

Comparison Chart

AbsorbanceTransmittance
DefinitionAbsorbance is the capacity of the substance to absorb a light falling on its surface.Transmittance is the ratio of light passing through the surface of the object.
Inter-relationWhen all the light hitting the surface of the object is absorbed then the transmittance is 0% and the absorption is 100%.If all the light hitting the surface of an object passes through the object then transmittance is 100% and absorption will be 0%.
ValueLessMore
MeasuringAbsorption is a lesser value and requires laser and other such technologies for measurement.Transmittance can easily be measured using the physical equipment.

What is Absorbance?

The term absorbance holds concepts in various fields like physics, analytical chemistry and others; here we’ll be taking a general view about this concept. Following it, absorbance is the capacity of the substance to absorb a light falling on its surface. A general example will give you a better know about the concept of transmittance, in hotter regions the houses are painted in light colors like sky blue, white and peach, whereas the dark colors are strongly avoided, that is because the dark colors absorb more of the sunlight falling and gets more hotter than any light color. Absorbance is equal to the logarithm of the reciprocal of the transmittance. This can be further elaborated as when all the light hitting the surface of the object is absorbed then the transmittance is 0% and the absorption is 100%. Therefore, it can be said that both these concepts are exactly opposite to each other. No manual equipment can tell about the actual absorbance value of an object as it is quite low, to get an accurate measurement of the absorption quantity, laser based techniques are considered one of the most accurate. The method through which absorption is being measured is called absorption spectroscopy. When the absorbance of the object is to be measured using spectrophotometer, absorbance can be defined as Log­10 (I0/I), where I0 is the intensity of the incident light ray, and I is the intensity of transmitted light.

What is Transmittance?

The term transmittance holds concepts in various fields like physics, analytical chemistry and others; here we’ll be taking a general view about this concept. Transmittance is the ratio of light passing through the surface of the object, when it is denoted in percentage with respect to the total intensity of light, then it is called percentage transmittance. Actually transmittance is the ratio between the Intensity of transmitted light I and the intensity of incident light I0. More the light passing through the object, more the transmittance, less the light passing through the object, less the transmittance. Unlike absorbance, transmittance can also be measured using the normal equipment.

Absorbance vs. Transmittance

  • Absorbance is the capacity of the substance to absorb a light falling on its surface, whereas, transmittance is the ratio of light passing through the surface of the object.
  • When all the light hitting the surface of the object is absorbed then the transmittance is 0% and the absorption is 100%, on the other hand, if all the light hitting the surface of an object passes through the object then transmittance is 100% and absorption will be 0%.
  • Absorbance gives the percentage in accordance with the light being absorbed with respect to the total intensity of light falling on the object, whereas transmittance gives the percentage in accordance with total light passing through the object surface with respect to the total intensity of light falling on object.
  • The value of absorption is relatively low as compare to the transmittance. Generally, absorption always have a lower value than 1.
  • Absorption is a lesser value and requires laser and other such technologies for measurement, on the other hand, transmittance can easily be measured using the physical equipment.
Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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