Explanation

(b) The impedance of R – C circuit for frequency $f_{1}$ is
$Z_{1} = \sqrt{R^{2} + \frac{1}{4\pi^{2}f^{2}C^{2}}}$
The impedance of R – C circuit for frequency 2$f$ is
$\ Z_{2} = \sqrt{R^{2} + \frac{1}{4\pi^{2}{(2f}^{2})C^{2}}}$
or $Z_{2} = \sqrt{R^{2} + \frac{1}{16\pi^{2}f^{2}C^{2}}}$
$\ $Then,$\ \ \ \ \ \ \ \ \ \frac{Z_{1}^{2}}{Z_{2}^{2}} = \frac{R^{2} + \frac{1}{4\pi^{2}f^{2}C^{2}}}{R^{2} + \frac{1}{16\pi^{2}f^{2}C^{2}}}$
Or $\frac{Z_{1}^{2}}{Z_{2}^{2}} = \frac{1 + \frac{1}{4\pi^{2}f^{2}C^{2}R^{2}}}{1 + \frac{1}{16\pi^{2}f^{2}R^{2}C^{2}}}$
Values are greater than 1 then $\frac{Z_{1}}{Z_{2}} =$ lies between 1 and 2.