Why if you actually look at a mirror is it blurred, but you need to look beyond it although there is nothing there to see your reflection clearly?

Question

Feels like a deep metaphor for something

In: Physics

Answer 1

A reflection preserves the relative direction and angle of the light. This means that the focus distance is preserved for objects you see reflected. Imagine you’re 1m from a mirror and there’s an object behind you, 3m from the mirror. To focus on the object you need to focus as if for 4m. To focus on the mirror you need to focus 1m away. So you won’t be able to focus on both the mirror and the object at the same time, especially in dim conditions when focussing needs to be more precise.