Question

How do I solve?

Answer 1

Given

light ray strikes the oil surface say from the air is 61.0 degrees and

inside it moves with an angle is 38.3 degrees

refractive index of air is n_a = 1.00

From Snell's law or law of refraction

   n_a *sin theta_a = n_b *sin theta_b

where n_a is the refractive index of the medium 'a'
and n_b is the refractive index of the medium 'b'

   sin theta_a is the angle of incidence and

   sin theta_b is angle of refraction

so n_b = (n_a* sin theta_a)/( sin theta_b )

n_b = (1*sin61.0)/(sin38.3)

n_b = 1.411

so the refractive index of the oil is n_b = 1.411