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8. Electromagnetic waves — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics8. Electromagnetic waves1 Mark
MCQ
Light is an electromagnetic wave. Its speed in vacuum is given by the expression
  • A
    $\sqrt {{\mu _o}{\varepsilon _o}} $
  • B
    $\sqrt {\frac{{{\mu _o}}}{{{\varepsilon _o}}}} $
  • C
    $\sqrt {\frac{{{\varepsilon _o}}}{{{\mu _o}}}} $
  • ✓
    $\frac{1}{{\sqrt {{\mu _o}{\varepsilon _o}} }}$
✓

Answer

Correct option: D.
$\frac{1}{{\sqrt {{\mu _o}{\varepsilon _o}} }}$
d
${\mu _0} = 4\pi \times {10^{ - 7}},\,{\varepsilon _0} = 8.85 \times {10^{ - 12}}\frac{{N{\rm{ - }}{m^2}}}{{{C^2}}}$
so $c = \frac{1}{{\sqrt {{\mu _0}{\varepsilon _0}} }} = 3 \times {10^8}\frac{{meter}}{{sec}}.$

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