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8.Electromagnetic waves
easy
The speed of electromagnetic radiation in vacuum is
A
${\mu _0}{ \in _0}$
B
$\sqrt {{\mu _0}{ \in _0}} $
C
$\frac{1}{{{\mu _0}{ \in _0}}}$
D
$\frac{1}{{\sqrt {{\mu _0}{ \in _0}} }}$
Solution
Maxwell deduced that the speed of propagation of an electromagnetic wave through a vacuum is entirely determined by the constants $\mu_0$ and $\epsilon_0$ as the following:
$c=\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$
We know that $\mu_0=4 \pi \times 10^{-7}\,Ns ^2 C ^{-2}$ and $\epsilon_0=8.854 \times 10^{-12}\, C ^2\, N ^{-1} \,m ^{-2}$ which gives:
$c =\frac{1}{\sqrt{4 \pi \times 10^{-7} 8.854 \times 10^{-1.12}}}=2.998 \times 10^8\,m / s$
Standard 12
Physics
