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

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

Step-by-step 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.

Answer 2

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

Step-by-step explanation:

It is given that,

Wavelength of Argon laser,
`\lambda=5* 10^2\ nm=5* 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=(c)/(n)`

`c_f=(3* 10^8\ m/s)/(1.46)`

`c_f=2.05* 10^8\ m/s`

or

`c_f=2.1* 10^8\ m/s`

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