Final answer:
A light ray reflected from a mirror changes direction by 2θ when the mirror is rotated by an angle θ, due to the Law of Reflection.
Step-by-step explanation:
In a laser light show, mirrors are often used to create dynamic visual effects by reflecting laser beams. According to the Law of Reflection, the angle at which the light ray arrives at the mirror (the angle of incidence) will be equal to the angle at which it leaves (the angle of reflection), measured from a line perpendicular to the surface of the mirror (the normal).
If the mirror itself is changed in its orientation by an angle θ, the reflected ray's direction changes by twice that angle, 2θ, because both the angle of incidence and reflection have changed by θ, causing the reflected ray's direction to be offset by double the mirror's rotation. This principle is crucial for the accurate control of the light path in laser light shows.