Final answer:
Movable control surfaces on guided munitions are used to direct and focus the munition towards a target, adjusting the trajectory during flight and maintaining precision.
Step-by-step explanation:
The purpose of the movable control surface on guided munitions is to control the direction of the munitions as they move towards their target. These control surfaces are crucial for the precision of the munitions, as they can be adjusted during flight to alter the trajectory. Additionally, the surfaces help to focus the munitions and ensure that they maintain a steady path by overcoming any internal repulsion of like charges. This is particularly relevant for munitions that rely on electromagnetic forces, where charged particle beams must be directed precisely.