Question

For a transparent medium relative permeability and permittivity, $\mu_ r$ and $\epsilon_{r}$ are $1.0$ and $1.44$ respectively. The velocity of light in this medium would be,

• A. 2.5 × 10$^8$ m/s
• B. 3 × 10$^8$ m/s
• C. 2.08 × 10$^8$ m/s
• D. 4.32 × 10$^8$ m/s

Answer 1

Answer: (A)

$ v = \frac{1}{\sqrt{\mu \epsilon}}$
$ = \frac{1}{\sqrt{\mu_{r} \epsilon_{r} \mu_{0} \epsilon_{0}}} $
$= \frac{3\times10^{8}}{\sqrt{1.44}} $
$ = \frac{30}{12} \times 10^{8} $
$= 2.5 \times10^{8} ms^{-1}$