Why ‘Objects In The Mirror Are Closer Than They Appear’?

Since it has a curved surface (unlike a regular mirror which has a plain surface), it reflects light and consequently displays images in a different manner.

There is more than one use of a side-view mirror: you can check out how your hair looks (most people do it too, don’t worry) or you can use it to look at some noteworthy feature on the road that your friends pointed at on a long drive.?

Oh right, you can also keep track of the vehicles on that side of your car.

It’s a good bet that people sitting in any vehicle spend a decent amount of time looking at the mirror, which always says, ‘Objects in the mirror are closer than they appear.’ Why do all side-view mirrors say that? And what does that warning really mean?


Recommended Video for you:

If you wish to buy/license this video, please write to us at admin@scienceabc.com.

A Safety Warning

The phrase ‘Objects in the mirror are closer than they appear’ is actually a safety warning that is printed/engraved on passenger side mirrors (or even driver side mirrors in some countries). It means exactly what it says; the objects (in this case, usually other vehicles) are actually closer than they appear to be in the mirror.

You must have observed this many times yourself. When you look at the image of an object in the side mirror and then turn backwards and glance at the object itself; you will find that the object is much closer than it appeared in the mirror.

How Does This Happen?

The appearance of the objects in the mirror is just another example of how the world of optics works. Perhaps you know this already, but the ‘mirror’ in the side mirror is not just a plain mirror (like the one you have in your bathroom), but is actually a convex mirror – a mirror that bulges towards you. Since it has a slightly curved surface (unlike a regular mirror, which has a flat surface), it reflects light differently, and consequently displays images in a different manner.

Image Formation in a Convex Mirror

Image formation by a convex mirror

Image formation by a convex mirror

When a light ray (from an object) falls near the center of a convex mirror, it’s path remains almost unaltered. However, if the light ray falls on the curved edges, the farther outward the light will bounce and spread out in all directions before reaching your eyes. Images form (or appear to form) where light rays from different directions intersect each other (at a focal point), but for diverging light rays, this would only be possible if they were to continue ‘through’ the mirror.

This is why the vehicles that you see in the side mirror seem to be ‘further inside’ the mirror (depending on the actual distance of the vehicle on your side). This is the reason why objects in the mirror look smaller and more compressed, and appear farther away than they actually are.

To cut a long story short, the image of the car that reaches your eyes (when you look at the mirror) is not exactly the same car that reflected the light in the first place.

Why can’t we use a plane mirror as a side mirror?

difference in the image formation by mirrors

Difference in the image formation of different mirrors (Image Source: www.physics.wisc.edu)

We can, but it wouldn’t be a good idea; a plane mirror shows images of the objects that are right in front of it. In other words, it would definitely show the objects in the mirror at the same distance as they actually are, but it wouldn’t reflect a large area next to the car, leaving a huge (and dangerous) blind spot. A convex mirror, on the other hand, covers a much wider area and has a much smaller blind spot, but comes with the drawback of giving a ‘false distance’.

convex mirror

Why do you think they put convex mirrors at turns and intersections? (Credit: Pedro Nogueira/Shutterstock)

It’s a safety trade-off, but from the overwhelming use of convex mirrors in our automobiles, it seems like the car industry made the right choice. Just be careful out there on the road!

Suggested Reading

Was this article helpful?
YesNo
Help us make this article better
Scientific discovery can be unexpected and full of chance surprises. Take your own here and learn something new and perhaps surprising!

Follow ScienceABC on Social Media:

About the Author

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spearheads the content and editorial wing of ScienceABC and manages its official Youtube channel. He’s a Harry Potter fan and tries, in vain, to use spells and charms (Accio! [insert object name]) in real life to get things done. He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does. A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life… in this universe, at least.

.
Science ABC YouTube Videos

  1. Neutron Stars Explained in Simple Words for LaymenNeutron Stars Explained in Simple Words for Laymen
  2. How Robert J. Oppenheimer became the ‘Father of the Atomic Bomb’How Robert J. Oppenheimer became the ‘Father of the Atomic Bomb’
  3. Higgs Boson (The God Particle) and Higgs Field Explained in Simple WordsHiggs Boson (The God Particle) and Higgs Field Explained in Simple Words
  4. Slowing or Reversing Aging: Can We Live for 180 years?Slowing or Reversing Aging: Can We Live for 180 years?
  5. Detectives Use this Simple Technique to Find Your Fingerprints (Even AFTER You Have Wiped Them Off)!Detectives Use this Simple Technique to Find Your Fingerprints (Even AFTER You Have Wiped Them Off)!
  6. Why is a Circle 360 Degrees, Why Not a Simpler Number, like 100?Why is a Circle 360 Degrees, Why Not a Simpler Number, like 100?
  7. Quantum Mechanics Explained in Ridiculously Simple WordsQuantum Mechanics Explained in Ridiculously Simple Words
  8. Do Fish Get Thirsty and Do They Need to Drink Water?Do Fish Get Thirsty and Do They Need to Drink Water?