Explain why calibration curves absorbance versus concentration may deviate from a straight line when a< 0.1 and when a> 1

Due to the inability of the measuring equipment to differentiate the transmittance when the value of the absorbance falls below 0.1 or above 1.

Explanation:

Generally, measuring equipment is used to record the spectroscopy measurement of a substance in terms of the absorbance (A) or a percentage of the transmittance (T). These two variables are related mathematically as:

A = -log T

The relationship can also be shown using a graphical representation and it normally follows a straight line. However, when the value of the absorbance falls below 0.1 or above 1, the plot deviates from the normal straight-line curve due to the inability of the measuring equipment to differentiate the transmittance.  

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