Question

The speed of electromagnetic waves in a medium depends on the ________.

• A. intensity of the wave
• B. initial phase of the wave
• C. permittivity and permeability of the medium
• D. energy it carries
• E. reflectivity of the medium

Hint:

In a vacuum, $c = \frac{1}{\sqrt{\mu_0\epsilon_0}} \approx 3 \times 10^8$ m/s.

Answer 1

The Correct Option is C

Step 1: Concept
The speed of electromagnetic waves in any medium is determined by the physical properties of that medium.

Step 2: Meaning
The velocity $v$ is given by the formula $v = \frac{1}{\sqrt{\mu\epsilon}}$, where $\mu$ is permeability and $\epsilon$ is permittivity.

Step 3: Analysis
Unlike mechanical waves, EM waves do not require a material medium, but their speed changes based on the electrical ($\epsilon$) and magnetic ($\mu$) constants of the space they occupy.

Step 4: Conclusion
Thus, the speed depends strictly on the permittivity and permeability of the medium. Final Answer: (C)