A coaxial cable with an inner diameter of 1 mm and outer diameter of 2.4 mm is filled with a dielectric of relative permittivity 10.89. Given μ₀ = 4π × 10^-7 H/m, \(\varepsilon_0=\frac{1}{36 π \times 10^9}\) F/m. The characteristic impedance of the cable is 

Inductance unit per length of coaxial cable:

L = \(\frac{40}{2\pi}ln \frac {b}{a}\)

Capacitance unit per length of coaxial cable:

C = \(\frac{2\pi\varepsilon_0\varepsilon_r}{ln(\frac{b}{a})}\)

Characteristics impedance of the cable is given as:

Z₀ = \(\sqrt\frac{L}{C}\) = \(\sqrt\frac{\mu}{\varepsilon_0\varepsilon_r}[\frac{1}{2\pi}ln(\frac{b}{a})]\)

= \(\frac{120\pi}{2\pi} \times \frac{1}{\sqrt{10.89}}ln(2.4) = 15.91\)

= 16 Ω

Here, option 4 is correct.