The relative permittivity of distilled water is 81. The velocity of light in it will be: (Given μ r = 1) (a) 4.33 × 107 m/s (b) 2.33 × 107 m/s (c) 3.33 × 107 m/s (d) 5.33 × 107 m/s

Answer: (c). v = (c)/(√(μrεr)) = 3 × 10⁸√(81). v = 3 × 10⁸9 = 3.33 × 10⁷ m/s. So the answer is (c) 3.33 × 10⁷ m/s.

The relative permittivity of distilled water is 81. The velocity of… | JEE Main 2021 (27 Jul, Shift 1)

Q17JEE Main 2021 · 27 JUL · SHIFT 1Easy

Speed of EM Waves in a Medium

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

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Answer: (c)

$v = \dfrac{c}{\sqrt{\mu_r\varepsilon_r}} = \dfrac{3 \times 10^{8}}{\sqrt{81}}$ .
$v = \dfrac{3 \times 10^{8}}{9} = 3.33 \times 10^{7}$ m/s.
So the answer is (c) $3.33 \times 10^{7}$ m/s.