Answer:
a
The the speed of light in the gemstone is
b
The unreasonable thing about this is that the speed of ligth in the gemstone is too low
the speed is 19% of the speed of light which is very low
c
One main unreasonable or inconsistent factor is that the assumption that the differnce between the angle of incidence and angle of refraction is very large
Explanation:
From the question we are told that
The angle of incidence
The angle of refraction
From Snell's law we have ,
Where is the refractive index of the first medium (water) with a constant value of
is the refractive index of the second medium (gem stone)
is the angle between the beam and perpendicular surface of the first medium
is the angle between the beam an the perpendicular surface of the second medium
Making the the subject of the formula
Generally refractive index of a material is mathematically represented
Where c is the speed light
v is the speed of light observed in a medium
Making v the subject
substituting value for gem stone