How do you find an angle of refraction after a ray of light is incident into a material?

When light passes from one medium to another, refraction occurs. Refraction is the bending of the light's path due to a change in speed upon crossing the medium interface. For example, when the sun's light crosses from the atmosphere into a body of water, or when light strikes the glass pane of a window. If we know the angle of incidence and the index of refraction of both mediums, we can use Snell's law to calculate the angle of refraction.

Snell's Law:

`Ni*sin(thetai) = Nr*sin(thetar)`

where

Ni = the refractive index of the incident medium,

Nr = the refractive index of the refractive medium,

`thetai` = the angle of incidence, and

`thetar` = the angle of refraction. 

Solving this equation for the angle of refraction yields:

`thetar = sin^(-1)((Ni*sin(thetai))/(Nr))`