Yes, and all the light will be bouncing off a flat plane, so there shouldn't be any depth.
If the mirror wasn't a mirror, then it would look like a flat plane.
But everything you see in a mirror has depth, doesn't it? Your own face looks 3D, right? You reach towards your reflection, and your reflection's hand reaches towards you in 3D, yes?
Just because the
surface is flat doesn't make its
optics flat.
Your face, shown on a video display, becomes 2D because all the points of light creating the visual appearance of your face are all
originating in a 2D plane. But a mirror is not the same as a video display.
[doublepost=1510170692][/doublepost]
You need to google how mirrors work...
Googling might make him think that the Earth is flat and Jenny McCarthy's boobs were always real.

[doublepost=1510172411][/doublepost]Let's get a little more
meta here...
To you, a person, a mirror is "flat" -- because you know it's a mirror. You know the definition of the word "mirror". You know that it's a piece of reflective glass, mounted on a wall, where you can get a better look at the hairs hanging out of your nose.
To an array of scattered light beams and a couple cameras, it's an unusually deep hole in an otherwise solid surface. The camera's "brain" has no
context -- it doesn't know that it's looking at a pane of glass with a reflective backing. All it knows is, the distances of the surfaces it can
visually resolve, such as the towel rack on the opposite wall of your bathroom, are farther away.
So what?
When the FaceID array sees your face in a mirror, it doesn't know that it's looking at a mirror.
It has no knowledge of context. It only knows that your face is a little farther away than usual, but it's still your face, and unlike with a photograph, your nose appears a few inches closer to the camera than your ears do.