4. What will be the percentage transmission when absorbance is 1, 2 and 3, respectively?
   (1) 10, 1, 0.1 (2) 1, 10, 100,
   (3) 0.2, 0.1, 0 (4) 20, 10, 0

Correct Answer:

(1) 10, 1, 0.1

Topic Explanation: Relationship Between Absorbance and Transmission

Absorbance (A) and percentage transmission (%T) are key concepts in spectrophotometry, used widely for quantifying biomolecules, monitoring reaction progress, and protein/nucleic acid analysis.

Definitions:

• Absorbance (A): A measure of how much light is absorbed by a sample.

• Transmittance (T): The fraction of incident light that passes through the sample.

• Percentage Transmission (%T):
  , where      T=I/I0             T=I/I0                    (I = transmitted intensity, I₀ = incident intensity).

Mathematical Relationship:

Absorbance and transmission are related as:

A=−log⁡10(T)

=−log⁡10(%T100) 

A=−log10(T)

=−log10(100%T)

Rearrange to solve for %T:

%T=10−A×100

%T=10−A×100

For Absorbance Values:

• If A = 1:
  %T=10−1×100=0.1×100=10%T=10−1×100=0.1×100=10

• If A = 2:
  %T=10−2×100=0.01×100=1%T=10−2×100=0.01×100=1

• If A = 3:
  %T=10−3×100=0.001×100=0.1%T=10−3×100=0.001×100=0.1

So the answer matches option (1): 10, 1, 0.1.

Quick Reference Table

Why is this Important for CSIR NET, ICMR, DBT, IIT JAM, and MSc Entrance Exams?

Understanding the link between absorbance and transmission is essential for analytical techniques in biochemistry, molecular biology, and life sciences. Such calculations are frequently tested in national-level entrance and fellowship exams. Practicing these fundamentals boosts your accuracy in laboratory work and conceptual problems.

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