Answer:
The phenomenon that works here is called Total internal reflection
Explanation:
When the angle of incidence is increased past the critical angle, the refracted angle will not exit the medium and all incident light will reflect back off a boundary back into the first medium.
This phenomenon is called Total Internal Reflection. Total Internal Reflection will only occur with a large angle of incidence that is greater than the critical angle.
Now, when we talk about the second medium
using the Law of refraction
Sini/Sinr =refractive index of medium 2/ refractive index of medium1
when the light ray passes from denser medium to rarer medium TIR happens along with angle of incident should be greater than critical angle. In this case incident angle is 45 degrees
conclusion: medium 2 is rarer here than medium 1
