A light ray strikes a plane mirror at point P making an angle of 45∘ with the normal. Which of the following actions will CHANGE the plane of incidence?
a) Rotating the mirror about the normal at P while keeping the incident ray fixed
b) Translating the mirror parallel to its surface without any rotation
c) Rotating the incident ray about the normal at P while keeping the mirror fixed
d) Rotating the incident ray within its original plane while keeping the mirror fixed