Question

What is the difference between TIR and normal reflection?

Answer 1

TIR here stands for Total internal reflection and normal reflection denotes the basic reflection that we all see in our day to day lives when we stand in front of a mirror or any shining object. TIR demands some specific conditions to occur whereas reflection can occur at the interface irrespective of specific conditions.

Complete answer:
Let us examine what normal reflection is.
Normal reflection or reflection is bouncing back off the light ray after hitting any surface. Technically change the direction of a wavefront at an interface between two different media so that the wavefront returns to the medium from which it originated.
Now let us see what total internal reflection is.
Total internal reflection is the phenomenon of bouncing back of light in the same medium after striking the boundary of a rarer medium. This happens when the angle of refraction exceeds $90^\circ$.
Now we will see the differences between total internal reflection and normal reflection.
Reflection of light occurs at any interface between two optical media whereas total internal reflection occurs only when at some specific conditions.
Reflection occurs for any angle of incidence between $0^\circ$ and $90^\circ$ whereas Total internal reflection only occurs when the angle of incidence is more than the critical angle between the two media.
In reflection a part of the light energy is reflected, some part of the light energy is scattered and some parts of it is refracted whereas in TIR all the light is reflected.
Reflection of light doesn't depend on the refractive index of the second medium whereas TIR depends on the refractive indices of both the media.

Note: Note that refraction is bending of light passing from one medium to another with different refractive indices whereas reflection is bouncing back of the light. The critical angle is the angle of incidence beyond which the light rays are not refracted in passing through a denser to a rarer medium but totally reflected.