# How do magnified mirrors work? **URL:** \ **Category:** Factual Questions\ **Created:** [May 20, 2006, 5:18am UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500 "2006-05-20T05:18:30Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![dnooman](https://avatars.discourse-cdn.com/v4/letter/d/839c29/32.png) [@dnooman](https://boards.straightdope.com/u/dnooman)\ **Post date:** [May 20, 2006, 5:18am UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/1 "2006-05-20T05:18:30Z")
I always thought mirrors were just reflective. Would these technically be lenses? ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [May 20, 2006, 9:13am UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/2 "2006-05-20T09:13:43Z")
No, if they were lenses the light would have to go \*\*through \*\*them. What causes the reflection to magnify is the fact that the mirror is slightly convex. If it were slightly concave, the reflection would be smaller. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 20, 2006, 4:01pm UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/3 "2006-05-20T16:01:08Z")
> [@panache45](#): > > What causes the reflection to magnify is the fact that the mirror is slightly convex. If it were slightly concave, the reflection would be smaller. You have that exactly reversed. Concave mirrors magnify your image, convex mirrors reduce it. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [May 20, 2006, 5:22pm UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/4 "2006-05-20T17:22:03Z")
> [@dnooman](#): > > I always thought mirrors were just reflective. Would these technically be lenses? The principle is somewhat similar in effect, but different in execution. Lenses use optical-density refraction to bend light passing through them… because light behaves differently in glass than in air, light passing from air through a curved glass lens and back into air will emerge slightly bent. Polished metal surfaces will reflect light back without bending them - IF THE SURFACE IS PERFECTLY FLAT. Except, of course, that nothing is perfectly flat, so even regular mirrors will magnify or shrink slightly at certain spots, but the effect is so small as to not be noticed. Creating a mirror that is curved just so, will bend the light reflecting off of it in similar ways to a lens, (though I think not all the optical effects possible with lenses are possible with mirrors. Might be wrong about that. Hope this helps. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 20, 2006, 5:52pm UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/5 "2006-05-20T17:52:19Z")
> [@chrisk](#): > > …I think not all the optical effects possible with lenses are possible with mirrors. Might be wrong about that. For one thing, lenses and other optical components, such as prisms, which _refract_ light affect different wavelengths of light differently. Longer wave, redder light will refract less than shorter, bluer light. Mirrors, on the other hand, reflect at the same angle of deflection regardless of wavelength. As a result, glass lenses suffer from a problem called chromatic aberration whereas mirrors do not. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [May 21, 2006, 1:12am UTC](https://boards.straightdope.com/t/how-do-magnified-mirrors-work/357500/6 "2006-05-21T01:12:26Z")
> [@Q.E.D.](#): > > You have that exactly reversed. Concave mirrors magnify your image, convex mirrors reduce it. Damn! I tried reasoning it out, and came up with what you’d look like to your reflection, rather than vice-versa.