GATE 2022 IN – Question 51
Monochromatic light of wavelength 532 nm is used to measure the absorption coefficient of a material in a UV-Visible Spectrophotometer. The measured light intensity after transmission through a 1 cm thick sample of the material is 0.414 mW/cm2. For a sample of thickness 2 cm, the measured light intensity is 0.186 mW/cm2. The absorption coefficient (in cmିଵ) of the material is ________ (round off to two decimal places)
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Correct answer: 0.75 to 0.85
Explanation
Beer–Lambert law gives I2/I1=exp[−α(2−1)].
Therefore α=ln(0.414/0.186)=0.8001 cm⁻¹, or **0.80 cm⁻¹**. Incident intensity cancels in the ratio.