Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: chris on 17/02/2012 09:11:40

Title: Why do objects in the rear view mirror appear closer than they are?
Post by: chris on 17/02/2012 09:11:40
Is this an intentional aspect of mirror design? Why does it happen?
Title: Re: Why do objects in the rear view mirror appear closer than they are?
Post by: Geezer on 17/02/2012 10:02:19
errrr, I think you got it downside up.

The text on the mirror should say "Objects in mirror are closer than they appear"

It's because the (usually) nearside mirror is convex to increase its field of view. The idea is to make sure you are aware of any vehicles that might be sneaking up on your "inside" before you move back into the "slow lane".
Title: Re: Why do objects in the rear view mirror appear closer than they are?
Post by: imatfaal on 17/02/2012 10:32:07
The Geezer is right.  I offer this incontrovertible proof - well actually it's just a movie still
 [ Invalid Attachment ]
I still cannot embed pictures in the post without the workaround


Title: Re: Why do objects in the rear view mirror appear closer than they are?
Post by: Phractality on 17/02/2012 19:23:07
The image you see in a convex mirror is called a virutal image. The virtual image, which is located behind the mirror from your perspective, is closer than the actual object, so our eyes converge to a point which is closer than the object. If we could judge distance by convergence of your eyes, you'd think the object is closer than it actually is. However, the angular size of the virtual image is smaller than the angular size of the object. We tend to estimate distance by angular size rather than by the angle of convergence of our eyes, so the think the object is farther than it really is.
 Image source. (http://triplescience.com/test/ExamBoards/PHYSICS/AQA/13.4_MirrorsLenses.html)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Ftriplescience.com%2Ftest%2FExamBoards%2FPHYSICS%2FAQA%2FIMAGES%2Faqa_13.4%2F12ray-diagram-convex-2.gif&hash=ba0b4e380742ecc96597315f62577151)
Title: Re: Why do objects in the rear view mirror appear closer than they are?
Post by: SeanB on 17/02/2012 19:29:53
This as well....