When a light ray is incident at a boundary, the normal is an imaginary line perpendicular to the boundary
Refraction is the change of direction that occurs when a wave crosses a boundary.The change of direction occurs when light passes at an angle across a boundary between two transparent substances.If a ray box directs light into a rectangular glass block, when light passes from air to glass the ray of light is refracted towards the normal.When light passes from glass to air the ray of light is refracted away from the normal.
Refraction is the change of direction that occurs when a wave crosses a boundary.The change of direction occurs when light passes at an angle across a boundary between two transparent substances.If a ray box directs light into a rectangular glass block, when light passes from air to glass the ray of light is refracted towards the normal.When light passes from glass to air the ray of light is refracted away from the normal.