Question 107: EM waves

Question

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

Accepted Answer

The speed of light in a medium is given by the equation:
$$ v = \frac{c}{\sqrt{\varepsilon_r \mu_r}} $$
where:
$c$ is the speed of light in vacuum (approximately $3 	imes 10^8$ m/s),
$\varepsilon_r$ is the relative permittivity of the medium (in this case, distilled water, and is given as 81),
$\mu_r$ is the relative permeability of the medium (given as 1 for distilled water).
Substituting the given values into the equation, we get:
$$ v = \frac{3 	imes 10^8 \, 	ext{m/s}}{\sqrt{81 	imes 1}} $$
$$ v = \frac{3 	imes 10^8 \, 	ext{m/s}}{9} $$
$$ v = 3.33 	imes 10^7 \, 	ext{m/s} $$
So, the speed of light in distilled water is $3.33 	imes 10^7$ m/s.

Answer

4.33 $$	imes$$ 10
7
m/s

Answer

2.33 $$	imes$$ 10
7
m/s

Answer

3.33 $$	imes$$ 10
7
m/s

Answer

5.33 $$	imes$$ 10
7
m/s

EM waves

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

Choose the correct answer: