Answer:
θ_c = 53.65°
Step-by-step explanation:
The point after which the light ray had started reflecting internally will be when the reflecting angle is at 90°. The incident angle at this point is called the critical angle and this can be calculated through Snell's law as;
n1 sin θ_c = n2 sin 90
Where;
n1 is the refractive index of the medium through which the incident rays will pass through.
n2 is the Refractive index of the medium through which the refracted rays will pass through.
θ_c is the critical angle at which the incident ray will reflect totally internally.
Now, since sin 90 = 1
Thus;
n1 sin θ_c = n2
θ_c = sin^(-1) (n2/n1)
Now, we are told that the reflection travels in flint glass and reflected from water.
Thus, the first medium is flint glass and the second medium is water.
So, from tables,
Refractive index of flint glass; n1 = 1.655
Refractive index of water; n2 = 1.333
Thus;
θ_c = sin^(-1) (1.333/1.655)
θ_c = 53.65°