The question is asking about the behavior of a reflected ray when the mirror is rotated. Whenever a mirror is rotated, the reflected ray`s direction will change, but the size of the reflected ray will remain the same.

Option 1 and 2 suggest that the size of the reflected ray will increase or decrease respectively. This is incorrect because the size or length of a ray is not affected by the rotation of the mirror.

Option 4 suggest that the reflected ray will `flatten into a disk-like shape`. This is also incorrect because a ray, including a reflected one, maintains its linear nature and doesn`t become a `disk-like shape`, regardless of the mirror`s rotation.

Option 3 is correct as it suggests that the reflected ray will `maintain its size`. This is what actually happens - the size of the reflected ray remains unchanged despite the rotation of the mirror. The only change that occurs is in the direction of the reflected ray.