Rear view mirrors

AlchemistK

In rearview mirrors (convex mirrors) of vehicles it is stated that " Objects are closer than they appear".
But as we see in the ray diagrams of a convex mirrors, the image formed is closer to the mirror than the object so the image is closer than it actually wouldve have been in the case of a plane mirror, so it should have been that the objects are further away than they appear.

Yet the image we see is further away and the objects really are closer than they appear.(I tried it with an actual convex mirror)

Can anyone help me what is causing this??

jtbell

The image in a convex mirror is actually closer to you, but it is also much smaller than it would normally be, so your brain perceives it as being further away.

AlchemistK

So is the dimnished image formed enough to form the illusion of a further image?

jtbell

Yes. Suppose that you have a convex mirror with focal length -0.50 m, and an object with size 1.0 m is a distance 10.0 m from the mirror. Calculate the actual image location and size.

Now suppose you are standing a distance 1.0 m from the mirror (with the object 9.0 m behind you). What is the angular size of the image, as seen by you? How far away from you would it have to be, in order to have the same angular size, if it were 1.0 m high? (This is how far away it appears to be.)

Buckleymanor

It's daft when you ponder about this.
Surely it's a number of accidents waiting to happen,especialy if you havn't read the small print or interpreted it wrongly.

Redbelly98

Why do you say "waiting to happen"? Millions of these mirrors have been in use for several decades already. If, after all that time, we are still waiting for this to someday cause an accident, that only proves it is not a major problem.

If people need to gauge the distance to something accurately, I think they mostly look directly at it or use the central rear-view mirror (which is flat and does not distort the true distance). At least that's what I do.

Buckleymanor

I can't comment on the amount of accidents these mirrors have or havn't caused.So I at leaste don't know if these are or could become someones major problem.
It does seem silly though to be forced by some manufacturers to use a sight adjustment device.
Imagine if these same producers made it a requirement that everyone had to wear optical glasses to adjust there vision irrespective of the quality of there eyesight,before they were allowed to drive forewards in one of there vehicles.
It would be thought as ludicrous.
In effect though that is what they are imposing on drivers when they reverse.
If a driver can't see properly from a flat mirror he should get himself glasses not the car maker.

Doc Al

Realize that convex mirrors are only used for the passenger side view mirrors. The driver side mirror and inside rear view mirrors are flat. The use of a convex mirror for the passenger side mirror was a breakthrough; it offers a wider field of view, making it much easier to spot other cars sneaking up on your outside.

Buckleymanor

Which if true just confuses the issue and makes it even more daft.
Here in the U.K. all three of our vehicles have convex mirrors on the passengers side and drivers side, the rear view mirrors all appear to be flat, except for the Range Rover, which I am not sure if it has a true image or not.
I presume you are referring to cars in the U.S.A. which if true when I visit I must remember to stick my neck out of the window and risk a cricked one.

russ_watters

No, that's really not what is happening at all. The reason for the shape of the mirror has nothing whatsoever to do with the optics of you your eyesight, it is about the placement and geometry of the mirrors. In order to give you the same field of view with flat mirrors, they'd need to install more (or bigger) mirrors. These mirrors are not there to be "sight adjustment devices" like glasses, which obviously must be customized for each person's eyesight.

Buckleymanor

Sorry but any device that states.To my mind is some kind of sight adjustment device.
If you don't adjust reality to take into account of what you see when you are reversing you will crash.

Redbelly98

Do you drive, yourself? It sounds like you don't. But if you do, how about an honest answer: what is your experience with these mirrors? Do you find them to be problematic when you actually use them?

From my experience, as an actual driver, I can tell you that these mirrors are not a hazard, and the wider field of view they offer is truly a help.

Buckleymanor

Well if you bothered to read thread you would see that I mentioned we had three vehicles.
I suppose you could deduce from that I don't drive and just like to look at them.
As for problems when using these mirrors to be honest yes.

Redbelly98

Fair enough. How many accidents have you had because of these mirrors?

DaveC426913

Buckley: your assumptions about the purpose of side view mirrors is in error. This is also incidentally causing you be driving improperly.

Side view mirrors are NOT for the purpose of determining the DISTANCE to an object. They are simply there so that the driver can determine IF there is an object there AT ALL.

If the mirrors were not convex, the field of view that they displayed of what is behind the driver would be so narrow as to be useless (I've done this, it's useless). There are only two ways to see a large field of view: make much larger mirrors (both impractical AND dangerous), or have small mirrors show a wider field of view.

This makes sense. You are using them wrong.

Drivers manuals tell you that you do not TRUST your mirrors to give you the whole picture. It is your reponsibility to LOOK OVER YOUR SHOULDER.

russ_watters

I've never consciously adjusted reality when looking into a mirror but no doubt the wider field of view has helped. Under what circumstances have you found yourself making an adjustment and why? What would you suggest as an alternative to convex mirrors - huge mirrors on all cars?

I'm not going to argue about the definition of a term you made up: whatever you call them, they are very much unlike glasses.

Buckleymanor

Exactly couldn't agree more.So why the hell do car makers go to the bother of messing about with the field of view in the first place.
Do you reckon it might be a subtle ploy to force us into a position whereby we don't trust our mirrors and therefore this forces you to look over your shoulder.
Unfortunately the less subtle might not have read any manuals and expect to take what they see as expected.