Question

Light from a laser pointer is goes through a window composed of crown glass, which has an index of refraction of 1.523. What is the speed of the light while it is in the window glass

Answer 1

Answer:

1.97 * 10^8 m/s

Explanation:

Parameters given:

Refractive index, n = 1.523

Refractive index is the ratio of the speed of light in a vacuum to the speed of light in a specified medium.

When the medium is glass, the refractive index is given as:

n = Vv/Vg

Where Vv = velocity of light in a vacuum

Vg = velocity of light in glass

The velocity of light in a vacuum is 3 * 10^8 m/s. Therefore,

1.523 = (3 * 10^8)/Vg

Vg = (3 * 10^8)/1.523

Vg = 1.97 * 10^8 m/s

Answer 2

Answer:

1.97×10⁸ m/s

Explanation:

From Snell's Law,

Refractive index of glass = Speed of light in air/ speed of light in glass

R.I = N1/N2................ Equation 1

Where R.I = refractive index, N1 = Speed of light, N2 = speed of light in glass

Make N2 the subject of the equation

N2 = N1/R.I.................. Equation 2

Given: R.I = 1.523, N1 = 3×10⁸ m/s

Substitute into equation 2

N2 = 3×10⁸ /1.523

N2 = 1.97×10⁸ m/s

Hence the speed of light in the glass window = 1.97×10⁸ m/s