Thick convex mirror or a thin one for the anti-theft mirror?

[heavystray]

Did you read the posts above?
The telescope mirror is silvered on the front so the thickness of glass is irrelevant for image construction. There are no reflections due to the glass.

Yes, but i was actually referring to this post

If the exam question had been about an astronomical telescope with a back-silvered (concave, as it happens) mirror, the multiple reflections could have been relevant to the image quality. As it happens, the mirrors you see in supermarkets could well be surface silvered and plastic, in any case.

So, it's possible that the answer is thin bcs thin mirror would have less internal reflections?

 

[nasu]

Oh, but astronomical mirrors do not have silvered backs but fronts.

Yes, it may be that they refer to the multiple reflections produced by the glass, in the case of back silvered mirrors.
But I still think this is not an important point. The reflection from glass may be an order of magnitude weaker than the one from the metal.

 

[bubsir]

I can't say I read every comment so excuse me if I missed something. The terms "thick" and "thin" have special meaning when applied to lenses as there is an entire field of "thin lens" design techniques. But when it come to mirrors - to the best of my knowledge - there is only the physical thickness of a back side coated optic to consider. As just mentioned "The reflection from glass may be an order of magnitude weaker than the one from the metal." - in fact for a silver mirror it is about 4% vs 94% (~2% loss in the silver). However that is for normal incidence. At high angles (45 deg or so) the balance changes. By 60 degrees its more like 15% to 83% and get progressively worse. Most security/safety mirrors are front side (aluminum) coated polished metal or plastic.

 

[peterlonz]

It has taken many knowledgeable replies to determine that thickness means thickness.
The problem appears to be a very poorly worded exam question.
But it may not be so easily dismissed:
No student could be expected to answer on a logical basis, without more information particularly what is meant by a "security mirror".
So I would have expected any decent teacher to realize that many of the class could not adequately respond, & he or she should have prepared a full explanation, even to the point of providing a complete written answer.
Alas maybe the teacher was not at full strength on the subject.

 

[sophiecentaur]

With respect sophiecentur, astronomical mirrors are generally silvered on the front.

Yes. I know. And one good reason is to avoid multiple reflections. That was my point. Maybe I didn't write the comment well enough.

 

[_Anthony_]

sophiecentaur, Or maybe more likely I didn't read it right. I'm new here and I don't want to offend anyone, I've got lots of questions to ask the "knowledge database" donating their time. I apologize for the miscommunication.