Meaning of refraction

•   refraction of light is the change in direction or bending of the light as it enters from one medium to another.
•  It is caused by the change in the velocity in which the velocity of light is lower is an optically denser medium.
• Refraction is  described by snell’s law ,which states that when a ray of light travels from vacuum (or air) at an angle of incidence ,I and refracted into a medium at an angle of refraction ,r.
•  n= sin i / sin r