# Light Refraction Issues

## Light speed

1. In one experiment, light passes through a glass plate with velocity equal to . Knowing that the speed of light in vacuum is, what is the refractive index of glass?

The refractive index in a medium is defined as the quotient between the speed of light in vacuum and the speed of light in the medium in question, ie:

No unit is used for the refractive index as it lists two equal units (velocity).

2. The figure shows a monochromatic ray of light that propagates in the air at an angle of 30 ° to the surface. When the radius starts to fall on the other medium the observed refractive angle is 60 °.

From this information calculate:

(a) The refractive index of light in the second medium.

(b) The speed of light in this medium.

(a) To calculate the refractive index of the environment just apply Snell's Law:

As the angles and refractive index of the incident medium are known, just isolate what the problem requires:

(b) The speed of refracted light is calculated by defining the refractive index:

Where c =:

## Diopters

1. A fisherman spots a fish in a lake at an apparent distance of 0.5 m from the surface. Considering the air (n = 1) and water (n = 1.33) refractive indices, what should be the actual distance between the water surface and the fish?

From the description of the system, the problem addresses vision distortion due to light passing through two means of different refractive indices:

We can calculate the actual distance to the fish using the ratio:

Where h = 0.5 m:

Looking at the figure, we can conclude that x = H-h = 0.165 m.