Logical Specs: Why Numbers are Blurry in Rear-View Mirrors

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SUMMARY

The discussion centers on the optical phenomenon of blurriness when viewing objects in a rear-view mirror without corrective lenses. Users experience clarity for near objects but struggle with distance vision, particularly with items like number plates that are approximately 16 inches away. The explanation provided highlights that the image seen in a flat mirror is perceived as being behind the mirror, necessitating a different focus compared to direct viewing. This distinction is crucial for understanding why corrective lenses are needed for certain distances.

PREREQUISITES
  • Understanding of basic optics and vision correction
  • Familiarity with the properties of plane mirrors
  • Knowledge of how human vision accommodates different distances
  • Awareness of the differences between flat and curved mirrors
NEXT STEPS
  • Research the principles of optical accommodation in human vision
  • Explore the physics of light reflection in plane mirrors
  • Investigate the effects of corrective lenses on vision clarity
  • Learn about the characteristics and uses of curved mirrors in optics
USEFUL FOR

This discussion is beneficial for individuals experiencing vision issues, optometrists, and anyone interested in the science of optics and vision correction.

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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
 
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Look into a mirror, one at home preferably. 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.
 
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.

15120205.jpg


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

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