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A mirror flips left and right, but not up and down

physics.stackexchange.com

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Re: A mirror flips left and right, but not up and down

#71

Post by doyoulikeworms »

sixtofour wrote: post #66
doyoulikeworms wrote: post #22

Assuming a mirror's face is its front: Photons bounce off the right side of you, strike the left side of the mirror, and then reach your eyes. Similarly for the left side. Photons bounce off the top side of you, strike the top side of the mirror, and then reach your eyes. Similarly for the bottom side.

I think this explanation is based on the (erroneous) tendency of people to think of what they see in the mirror as themselves turned around. Look at the desk in front of you. The right hand drawer is near your right hand. The left hand drawer is near you left hand. Now why did you just call the right side of the mirror, which is near your right hand, as the left side?

It assumes that the mirror's face is its front, making the right side of the mirror near your left hand. I only described it this way to reduce word count. We can say something similar using your more precise terms-- "near left/right hand".

I did not describe the mirror "turning you around". If it was yourself turned around, you'd see photons from your doppelganger's right hand near your left (as is the case when you face someone). Since it's a reflection, which does not turn anything around (as you said), your image of your left hand is near your actual left hand. To wrap it all up-- the reflection of your head is near your head, and your feet is near your feet. This is why you are reversed left-right, and not top-down in a flat mirror.

Re: A mirror flips left and right, but not up and down

#72

Post by david927 »

RickHull wrote: post #43
ruibai wrote: post #26

Skipping all the details, it's because you have a left eye and a right eye, not an up eye and a down eye.

The effect does not go away if you only have (or use) one eye.

Turn the mirror 90 degrees and nothing happens. Turn your head 90 degrees and it flips up and down.

Re: A mirror flips left and right, but not up and down

#74

Post by Natsu »

InclinedPlane wrote: post #8

Mirror's don't flip left and right. We implicitly compare a mirror image to the original by rotating the object, and naturally we maintain top/bottom orientation, this gives the appearance of "flipping" the object left to right. However, if you use vertical rotation to super-impose the object on its mirror image you'll see that it seems to have been flipped top-to-bottom instead.

Or you can just put a mirror on the ceiling and look into it for a visual demonstration of it working the "other" way.

Re: A mirror flips left and right, but not up and down

#75

Post by majmun »

when you have mirror in front than, left and right are not changed on mirror image but front and back. including side mirror and bottom mirror it goes like this: Front miror: front/back:yes, top/down:no, left/right:no Side mirror: front/back:no, top/down:no, left/right:yes Bottom mirror: front/back:no, top/down:yes, left/right:no

so i guess this question is like asking: why is 1 + 1 always equals 3 but no 4?

such question can have two meanings:

1: person reqly thinks that 1+1 = 3, answare is in the mindset of person that asked question

2: person is just making sounds taht resembles those of human talk (like parrots) and this is not even question. but mimicing (common in nature)

Re: A mirror flips left and right, but not up and down

#77

Post by JonnieCache »

losvedir wrote: post #40

To go along with fun mirror-things to think about, how about this one: Stand in front of a mirror. Note the lowest point on your body that you can see in the reflection, whether it's your waist or thighs, or whatever. Now, no matter how close you get to the mirror or how far you step back, that will always be the lowest point on your body in the reflection. (e.g., you'll never be able to see your toes, if you couldn'…

LIES! I just tried this, the visible portion increased by about a 50cm when I stepped back about 3m.

I guess this is because my big mirror isn't exactly flat to the wall. Come to think of it, it isn't even completely flat.

Re: A mirror flips left and right, but not up and down

#79

Post by narcissus »

omaranto wrote: post #49
Jtsummers wrote: post #20

Earlier quoted context omitted.

The question itself stems from confusion about what's being seen. It's not uncommon, especially with children, for people to become slightly confused while using a mirror. For instance, on seeing some smudge on their left cheek trying to wipe it from their right cheek. Once they start moving of course the error becomes obvious. Their initial understanding of the image is really what the image would be if you had a ca…

I have this problem all the time! I even shave by touch and then check in the mirror whether I've missed a spot rather than shave while looking in the mirror because I can't avoid being confused about this. I can , while looking at the mirror, reason about which way I need to move my hand to get at a certain spot on my face's reflection, but it's much faster to stop looking at the mirror and let (correct) instincts k…

I had my tongue pierced a few years back and even now (not that I do it very often), when looking in a mirror to put the ball back on the 'stick' (I don't know what it's called!) I drive myself nuts.

In one hand I'm trying to hold/'point' the 'stick' and in the other hand, not only am I trying to get the ball to the end of the stick, but at the same time trying to rotate it so that the hole in the ball lines up with the end of the stick. Everything points, moves and rolls totally against what I think it should be doing.

I, like you, find it easier to just do away with the mirror and try and work it out myself.

Having said that, this whole conversation has made me really think about the mirror and so I'm hoping that next time, it won't be so hard!

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