\(\Rightarrow\)  \(I \propto {a^2}{n^2}\) 

\(\Rightarrow\)  \(\frac{{{I_1}}}{{{I_2}}} = {\left( {\frac{{{a_1}}}{{{a_2}}}} \right)^2} \times {\left( {\frac{{{n_1}}}{{{n_2}}}} \right)^2}\)

\( = {\left( {\frac{1}{2}} \right)^2} \times {\left( {\frac{1}{{1/4}}} \right)^2}\)

\(\Rightarrow {I_2} = \frac{{{I_1}}}{4}\)