Answer:
Option (B) is true
Explanation:
refractive index of water = n1
refractive index of air = na = 1
refractive index of oil = n2
When the ray goes from water to air
Use Snell's law
Let the angle of incidence is i
n1 Sin i = na x Sin r
For total internal reflection, r = 90°
n1 x Sin i = 1 x Sin 90
Sin i = 1 / n1 .... (1)
For water oil interface
angle of incidence is i and let the angle of refraction is r.
n1 x Sin i = n2 x Sin r
n1 x / 1 n1 = n2 Sin r (from equation (1)
Sinr = 1/n2