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DALeffler
2006-Jul-15, 01:07 AM
How is light reflected from a mirror and light reflected from a shiny metal surface differnt from each other?

I'm nearsighted - very - and noticed something odd.

If I take my glasses off in front of a mirror, the reflected light I see from objects behind me in the mirror are still completly out of focus even though the image in the mirror is right next to the image of my face, which is perfectly in focus if I'm close enough to the mirror.

Why is that?

But if I look at reflected light from a chromed(?) frying pan lid (curved surface, yup), the reflected images are sharp and clean. Reflected images from across the room that I could never distinguish without eye glasses - while small in the frying pan lid - are crisp.

So I carefully placed the frying pan lid onto the mirror next to the image of my reflected face: That's where the differences between the reflected images in the mirror and the frying pan are most evident.

Anybody kniow why?

My bet would be that people with normal vision see crisp images in the mirror and the frying pan lid, and, well, do ya? :)

01101001
2006-Jul-15, 01:53 AM
How is light reflected from a mirror and light reflected from a shiny metal surface differnt from each other?
They are the same. A mirror (http://en.wikipedia.org/wiki/Mirror) is most often just a piece of flat glass coated, usually on the back side to protect the coating, with a shiny metal, usually aluminum.

(But, the telescope makers here are usually playing with concave glass, and coatings on the near side so the light doesn't have to pass through that nasty glass.)


I'm nearsighted - very - and noticed something odd.

If I take my glasses off in front of a mirror, the reflected light I see from objects behind me in the mirror are still completly out of focus even though the image in the mirror is right next to the image of my face, which is perfectly in focus if I'm close enough to the mirror.

Why is that?
Those images of stuff behind your face are coming from a distance that is beyond your ability to focus.


But if I look at reflected light from a chromed(?) frying pan lid (curved surface, yup), the reflected images are sharp and clean. Reflected images from across the room that I could never distinguish without eye glasses - while small in the frying pan lid - are crisp.
Those virtual images (http://en.wikipedia.org/wiki/Virtual_image) of stuff behind your face are coming from a virtual distance that is within your ability to focus. If you back away from the convex mirror, you'll probably find distant virtual objects moving beyond your ability to focus.

The specular convex surface acts similar to the lenses in your prescription glasses.

yuzuha
2006-Jul-15, 05:55 AM
Also, the lid acts as a first surface mirror. Ordinary mirrors have the reflective coating on the back so you may be seeing a blurry double image from both the front and back surface of the glass.

PhantomWolf
2006-Jul-16, 11:17 PM
Anybody kniow why?

01101001 pretty much answered this, the pot lid is acting like a lens as it focuses the light rays to create a virtual image whereas a flat surface reflects the light rays directly back with no focal point to the image. Reflector telescopes use this exact principle to use a mirror rather than a lens to focus the image.

Here's a page (http://www.physics.mun.ca/~jjerrett/animations.html) that has links to some optics stuff