## 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.*