An ice cube (n = 1.31) has a layer of water (n = 1.33) on it. What is the critical angle for a ray in water trying to enter the ice?

(Unit=deg)

Given that,

The Refractive index of glass is

n (ice) = 1.31

The refractive index of water is

n (water) = 1.33

What is the critical angle?

From water to ice

Critical angle is given as.

Using Snell's Rule.

Sin (θc) = n1 / n2

for total internal reflection the incident ray is always in the denser medium! So, water is the more denser than ice.

Then,.

Sin (θc) = n (ice) / n (water)

Sin (θc) = 1.31 / 1.33

Sin (θc) = 0.98496

θc = arcSin (0.98496)

θc = 80.05°

The critical angle is 80.05°