Consider a convex lens with $$f$$ focal length in $$f$$ distance from a wall. Principle axis is perpendicular to the wall. A mirror is rotating with $$\omega$$ angular velocity so that axis of rotation is perpendicular to principle axis .
Parallel rays of light incident on the mirror. After reflecting the light ray and passing the lens , a spot is created on the wall. In this diagram , rays after reflection from the mirror is parallel to principle axis of the lens and the created spot on the wall in point $$F$$ is focal point. What is the velocity of spot exactly in this time ?