Question

An Argon laser (λ = 5.0×102nm) shines down a silica glass fiber-optic cable with index of refraction 1.46. What is the speed of the laser light, cf , in the cable? Select One of the Following:
(a) 1.5 × 108 m s
(b) 2.1 × 108 m s
(c) 3.0 × 108 m s
(d) 4.4 × 108 m

Answer 1

Answer:

The speed of the laser light in the cable, $c_f=2.1\times 10^8\ m/s$

Explanation:

It is given that,

Wavelength of Argon laser, $\lambda=5\times 10^2\ nm=5\times 10^{-7}\ m$

Refractive index, n = 1.46

Let $c_f$ is the speed of the laser light in the cable. The speed of light in a medium is given by :

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

$c_f=\dfrac{3\times 10^8\ m/s}{1.46}$

$c_f=2.05\times 10^8\ m/s$

or

$c_f=2.1\times 10^8\ m/s$

So, the speed of the laser light is $2.1\times 10^8\ m/s$. Hence, this is the required solution.

Answer 2

Answer:

2.1 x 10^8 m/s option (b)

Explanation:

refractive index of the fiber, n = 1.46

refractive index of air = 1

According to the definition of refractive index

Speed of light in vacuum / speed of light in fiber = n

speed of light in fiber = speed of light in air / n

                                   = ( 3 x 10^8) / 1.46 = 2.1 x 10^8 m/s

Thus, the speed of light in fiber is 2.1 x 10^8 m/s.