Answer:
Refractive index of the plastic = 1.46
Step-by-step explanation:
By Snell's law,

Here,
= Angle of incidence in medium 1 (Plastic)
= Angle of refraction in medium 2 (Water)
= Refractive index of medium 1 (Plastic)
= Refractive index of medium 2 (Water)
By substituting values in the formula,


= 1.46
Therefore, refractive index of the plastic = 1.46