Correct Answer - Option 4 : 1.31%
The external quantum efficiency is defined as:
\({\eta _e} = \frac{1}{{4{n^2}}}\frac{{4n}}{{{{\left( {n + 1} \right)}^2}}} = \frac{1}{{n{{\left( {n + 1} \right)}^2}}}\)
where n is the permittivity of the material.
\(n = \sqrt {{\epsilon_0}{\epsilon_r}} = \sqrt {12.9}\)
= 3.59
\(\% {\eta _e} = \frac{1}{{3.59{{\left( {3.59 + 1} \right)}^2}}} \times 100 = 1.31\%\)
