<P> Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface . If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle , the wave can not pass through and is entirely reflected . The critical angle is the angle of incidence above which the total internal reflection occurs . This is particularly common as an optical phenomenon , where light waves are involved , but it occurs with many types of waves , such as electromagnetic waves in general or sound waves . When a wave reaches a boundary between different materials with different refractive indices , the wave will in general be partially refracted at the boundary surface , and partially reflected . However , if the angle of incidence is greater ( i.e. the direction of propagation is closer to being parallel to the boundary ) than the critical angle -- the angle of incidence at which light is refracted such that it travels along the boundary -- then the wave will not cross the boundary , but will instead be totally reflected back internally . This can only occur when the wave in a medium with a higher refractive index ( n ) reaches a boundary with a medium of lower refractive index ( n ) . For example , it will occur with light reaching air from glass , but not when reaching glass from air . </P>
<P> Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface . If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle , the wave can not pass through and is entirely reflected . The critical angle is the angle of incidence above which the total internal reflection occurs . This is particularly common as an optical phenomenon , where light waves are involved , but it occurs with many types of waves , such as electromagnetic waves in general or sound waves . When a wave reaches a boundary between different materials with different refractive indices , the wave will in general be partially refracted at the boundary surface , and partially reflected . However , if the angle of incidence is greater ( i.e. the direction of propagation is closer to being parallel to the boundary ) than the critical angle -- the angle of incidence at which light is refracted such that it travels along the boundary -- then the wave will not cross the boundary , but will instead be totally reflected back internally . This can only occur when the wave in a medium with a higher refractive index ( n ) reaches a boundary with a medium of lower refractive index ( n ) . For example , it will occur with light reaching air from glass , but not when reaching glass from air . </P>
critical angle of an interface between a dense medium and air
critical angle of an interface between a dense medium and air
angle of incidence
angle of incidence