Total internal reflection can take only if

There is air above water. Total internal reflection may take place for a ray of light passing from water to air. If a glass slab is placed above water, is it possible for a ray to be totally reflected? Where will the total internal reflection take place?

Why will not the total internal reflection take place if light travels from a rarer medium to a denser medium?

What is total internal reflection of light ? What are the two essential conditions for total internal reflection to take place ?

Where the phenomena of total internal reflection can be observed ?

Total internal reflection takes place when the light ray travels from....