Physics of mirrors?

[mosdef]

Why do you see more or less of yourself depending how far or close to the mirror you are?

-mosdef

 

[ApacheXMD]

cuz light travels in a straight line and angle of incidence equals angle of reflection.
It's simply Huygen's Principle. Easy smeezy
😛

-patchy

 

[HomeBrewerDude]

you don't see more of your self, assuming your relative positions and angle stay constant.

 

[mosdef]

Do you mean by this that you are looking at the same angles, but because you are farther back these angles have a bigger impact?

-mosdef

 

[HomeBrewerDude]

try it... if you can't see your feet in a mirror, backing up or moving forward won't help.

 

[mosdef]

<< you don't see more of your self, assuming your relative positions and angle stay constant. >>



What do you mean by relative position and angle? For example, if I look right into the mirror with my face a few inches from the mirror, and then back up, I begin to see my body.

-mosdef

 

[br0wn]

Why is it that mirror appears to reverse left and right, but not up and down ?

For example, if you raise your left hand your reflection raises what appears to be his right hand.
However, when you tilt your head up your reflection does too, and
does not appear to tilt his head down.

 

[HomeBrewerDude]

No, you don't see more of your body as you back away from a mirror. This is a common misconception. I just tried it to make sure I wasn't full of crap...

 

[Descartes]

brown: It's because we visualize ourselves as being rotated on a vertical axis when we view ourselves in the mirror. The problem is that we're not being rotated at all. The left side of your face is still the left side of the mirror, and the right side is still the right. If instead we perceived ourselves to be rotated on a horizontal axis, we would get a different effect. It's just that our minds have a particular affinity for seeing things rotated on a vertical axis (we like to remain upright due to our cerebellum 🙂) as opposed to a horizontal axis.front->back.

 

[dopcombo]

brown: I have never thought about a mirror as reflecting a person.
You are mapped point to point into the &quot;3d space behind&quot; the mirror.

doesn't explain your philosophical qn though... 😛

 

[Descartes]

That's a common misconception. You're not mapped to anything, and certainly nothing &quot;behind&quot; the mirror. It's the perception that we have somehow rotated ourselves 180degrees on a vertical axis that leads to this misconception. It's simply easier for our minds to understand the idea of being rotated, and not reflected.

 

[HomeBrewerDude]

Yeah your visual perception centers of your brain can do some amazing things. For instance, if you put on a pair of glasses that inverts images, it wouldn't take too long before your brain adapted to an upside down visual field. In fact, you would become so adapted, that you would not even notice that you were seeing everthing upside down and when you removed the glasses then you would have to re-adapted to an inverted visual field.

 

[mosdef]

<< No, you don't see more of your body as you back away from a mirror. This is a common misconception. I just tried it to make sure I wasn't full of crap... >>



What's the significance of this fact (you don't see more of your body) and why do we have this misconception?

-mosdef

 

[HomeBrewerDude]

i don't know the significance...other than as a lesson in optics, but the misconception is probably based on our experience with having to retreat from a large object in order to be able to see it without moving the head.


EDIT: I have seen video of interviews with recent MIT graduates, asking if you can see your feet in a mirror if you back up and the over whelming majority of students said you could.