What is the primary purpose of a mirror on a meter?

The primary purpose of a mirror on a meter is to reduce parallax error. Parallax error occurs when an observer's line of sight is not perfectly aligned with the pointer on the scale of the meter. This misalignment can lead to inaccurate readings due to the displacement of the pointer in the observer's view.

By incorporating a mirror into the design, the user can look straight at the mirror's reflection of the pointer. This allows the observer to align their viewpoint directly with the scale, ensuring that the pointer is seen accurately at the true position, thus minimizing parallax error. This technique is particularly useful in precision measurements where accuracy is critical.

While enhancing brightness, supporting the pointer, and magnifying readings could be aspects considered in different contexts, they do not specifically address the main function of a mirror within a meter. The reduction of parallax error is essential for achieving precise and reliable measurements.