logical specs

specs

Hi, I hope you can answer this question that is baffling me.
I now require spectacles for driving; anything more than 20 feet away is a blur.
But my near vision is perfect, so fine print from a book is no problem.
So why, without my spectacles on and looking in a rear-view mirror, which is approx 16 inches away and at head height, are the number plates of the cars behind blurry?
If I then put my new specs on the number plates are perfectly clear.
I tried my own off the cuff experiment, and stuck a sticker on the rear-view mirror with some writing on it, and without glasses it was perfectly clear, when I tried my specs the sticker’s text became distorted.
Thank you in advance

Drakkith

Look into a mirror, one at home preferrably. Notice that you have to focus differently when you look at objects that are further or closer in the mirror. This is just like you would have to do if you turned around and looked at those same objects. The mirror doesn't make it look like the objects are the same distance away as the mirror is.

jtbell

The image that you see in a mirror is not in the plane of the mirror. It's behind the mirror, in fact it's the same distance behind the mirror as the original object is in front of the mirror.



This assumes a plane (flat) mirror. Curved mirrors are another matter.