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If the velocity of light in vacuum is $3 \times 10^{8} \mathrm{ms}^{-1}$, the time taken (in nanosecond) to travel through a glass plate of thickness $10 \mathrm{cm}$ and refractive index 1.5 is
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The correct answer is:
0.5
Given $v=3 \times 10^{8} \mathrm{ms}^{-1}, d=10 \mathrm{m}$ and $\mu=1.5$
Here, $t=\frac{d}{c / \mu}$
$$
t=\frac{10 \times 10^{-2}}{2 \times 10^{8}}
$$
$\left(\therefore \frac{c}{\mu}=\frac{3 \times 10^{8}}{1.5}=2 \times 10^{8} \mathrm{ms}^{-1}\right)$
$t=0.5 \times 10^{-9} \mathrm{s}$
Here, $t=\frac{d}{c / \mu}$
$$
t=\frac{10 \times 10^{-2}}{2 \times 10^{8}}
$$
$\left(\therefore \frac{c}{\mu}=\frac{3 \times 10^{8}}{1.5}=2 \times 10^{8} \mathrm{ms}^{-1}\right)$
$t=0.5 \times 10^{-9} \mathrm{s}$
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