Question

The dielectric constant of air is $1.006$ . The speed of electromagnetic wave travelling in air is $a\times {{10}^{8}}m{{s}^{-1}},$ where a is about

• A. 3
• B. 3.88
• C. 2.5
• D. 3.2

Answer 1

Answer: (A)

3

Answer 2

For an electromagnetic wave (in vacuum), Velocity
$c=\frac{1}{\sqrt{{{\mu }_{0}}{{\varepsilon }_{0}}}}=3\times {{10}^{8}}m{{s}^{-1}}$
Air acts almost as vacuum, hence $a=3(approx)$