One laboratory group repeated the same experiment described by others with the i

Question

One laboratory group repeated the same experiment described by others with the identical bacterial isolate and the same growth medium and conditions used but were unable to achieve the same O.D. at 600 nm. What is the LEAST likely cause for this discrepancy of turbidity measured? The two labs varied with 1000 m elevation and did not consider the influence of pressure. One lab subtracted the yellow color of the growth medium away from the final turbidity reported whereas the other lab used colorless water. One lab used 16 mm wide test tubes and the other used 18 mm wide test tubes. One lab vigorously dispersed the biofilm-forming bacteria with and the other did not.

Explanation / Answer

We know that,

OD = A/L where OD = optical density, A= absorbance, L=thickness of sample

From this we can easily say that optical density inversely proportional to the thickness of the sample.

That's why the O.D value of one lab after using 16 mm wide test tube is higher than the another lab who use 18 mm wide test tube.

So, the ans is option 3.

But if we use colorimeter to detect O.D the ans will be 2 because colorimeter determine the concentration of coloured compond in solution.

So, accumulating the above data we can say that the ans will must be either 2 or 3 depending on the technique [either colorimeter or spectrophotometer respectively ] we use to determine O.D.

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