Answer
$\frac{I_2}{I_1}=0.49$
$\frac{I_3}{I_1}=0.36$
$\beta_2=-3.10dB$
$\beta_3=-4.44dB$
Work Step by Step
$I=2\pi^2\rho vf^2A^2$
$\frac{A_2}{A_1}=\frac{0.35}{1}=0.35$
$\frac{f_2}{f_1}=2$
$\frac{A_3}{A_1}=\frac{0.15}{1}=0.15$
$\frac{f_3}{f_1}=4$
$\frac{I_2}{I_1}=\frac{f_2^2A_2^2}{f_1^2A_1^2}=2^2(0.35)^2=0.49$
$\frac{I_3}{I_1}=\frac{f_3^2A_3^2}{f_1^2A_1^2}=4^2(0.15)^2=0.36$
$\beta_2=10\log\Big(\frac{I_2}{I_1}\Big)=10\log(0.49)=-3.098dB$
$\beta_3=10\log\Big(\frac{I_3}{I_1}\Big)=10\log(0.36)=-4.437dB$
