the critical angle of the incident ray is the angle that light

Question

a. needs to reflect straight back upon itself

b. needs to bend around an object

c. needs to refract along the boundary of a medium

d. would take when it passes straight through an object

Answer 1

The critical angle of incidence occurs when the incident light does not penetrate into the next medium.  The light refracts along the boundary that separates the two mediums.  The correct answer is (C).  This can only happen when the light tries to cross into a medium of lower refractive index.  It is a consequence of Snell's law.  Have you seen Snell's law in your physics class?  It provides a clear way to understand this.