We know, the refractive index of air is 1, Let the refractive index of medium be η
The angle of incidence is given as 450
For total internal reflection, the angle of refraction must be 900
For total internal reflection, η×sin45≥1×sin90
⇒n≥√2
⇒n≥1.414
So the possible value of η is 1.5,
Therefore the correct option is B.