Question

The relative permittivity of distilled water is $81$. The velocity of light in it will be :
(Given ${\mu }_r=1$)

• A. $4.33\times {10}^7\text{m/s}$
• B. $3.33\times {10}^7\text{m/s}$
• C. $5.33\times {10}^7\text{m/s}$
• D. $2.33\times {10}^7\text{m/s}$

Answer 1

The correct option is B $3.33\times {10}^7\text{m/s}$

The velocity of light in the medium is given by,

$v=\frac{c}{\sqrt{{\mu }_r{\epsilon }_r}}$

Where,
${\mu }_r=$ relative permeability $=1,$
${\epsilon }_r=$ relative permittivity $=81$

$v=\frac{3\times {10}^8}{\sqrt{1\times 81}}$

$\therefore v=3.33\times {10}^7\text{m/s}$

Hence, option $\left(\text{C}\right)$ is correct.