Question

If you want to delay a pulse of light in a laser experiment, you can send the light through a long coil of fiber optic cable. Light travels somewhat slower in the glass core of a fiber than it does in vacuum. We will approximate the speed of light in the fiber as 2.04 x 10⁸ m/s. What length of fiber (in meters) does the light travel in 168 ns?

Answer 1

Time taken by a certain particle to cover a certain length or distance in particular speed is given by the formula

$Distance = speed \times time$

Here, the particle is light

Speed of light in optical fibre $= 2.04 \times 10^{8} \; m/s$

Amount of time need to be delayed = 168 ns

$= 168 \times 10^{-9} \; s \\ = 1.68 \times 10^{-7} \; s$

The length of optical fibre required = Speed of light in optical fibre x amount of time to be delayed

$= 2.04 \times 10^8 \times 1.68 \times 10^{-7} \; m \\ = 34.27 \;m$

Answer: 34.27 m