Question

The time taken by a monochromatic light to travel A certain distance in air in 9 into 10 to power minus 6 second the time taken by light to travel the same distance in water of refractive index 4 by 3 is option A 12 second option B 12 Mu second option C 27 by 4 mu seconds and option D 27 by 2 mu seconds

Answer 1

Answer: (B). The time taken by light is $t_{2}= 12\times10^{-6} s$.

Explanation:

Given that,

Time $t_{1}=9\times10^{-6}second$

Refractive index $n=\dfrac{4}{3}$

Let us considered air be the medium one and water be the medium second.

We know that,

The refractive index is the ratio of the speed of light and phase velocity of the light in the medium.

$n = \dfrac{c}{v}$

The refractive index is

$n_{12}= \dfrac{v_{2}}{v_{1}}$

We know , velocity = distance /time

Therefore,

$n_{12}= \dfrac{t_{2}}{t_{1}}$

Put the value of $n_{12}$ and $t_{1}$

$\dfrac{4}{3}= \dfrac{t_{2}}{9\times10^{-6}}$

$t_{2}= \dfrac{36\times10^{-6}}{3}$

$t_{2}= 12\times10^{-6} s$

Hence, The time taken by light is $t_{2}= 12\times10^{-6} s$.

Answer 2

correctAnswer:

Explanation:

e=mc^2