Question

The intrinsic impedance of free space is _________.

• A. 76 $\Omega$
• B. 73 $\Omega$
• C. 120$\pi$ $\Omega$
• D. 300 $\Omega$

Hint:

Intrinsic impedance of vacuum = \(120\pi \Omega \approx 377 \Omega\); it's a core EM constant for wave propagation.

Answer 1

The Correct Option is C

The intrinsic impedance of free space (\(\eta_0\)) is the ratio of the electric field (E) to the magnetic field (H) in a plane electromagnetic wave traveling through a vacuum: \[ \eta_0 = \sqrt{\frac{\mu_0}{\varepsilon_0}} = 120\pi \ \Omega \approx 377 \ \Omega \] Where:
\(\mu_0 = 4\pi \times 10^{-7} \ \text{H/m}\) (permeability of free space)
\(\varepsilon_0 = 8.854 \times 10^{-12} \ \text{F/m}\) (permittivity of free space)
This value is fundamental in electromagnetic theory, as it defines how EM waves propagate in free space.
Incorrect Options:
(1), (2), (4): These values are approximations or incorrect guesses. Only \(120\pi\) is accurate and physically defined.
Final Answer: (3) 120$\pi$ $\Omega$