Re: Help: rear view mirror optics (fwd)

[Chuck Britton <britton@NCSSM.EDU>]

It is definitely a WEDGE of glass. Touch a pencil tip to the surface
to gauge the thickness.

BUT - I can use the night-time dimming feature EITHER by sending the
bright image ABOVE OR BELOW my eyes.

My wife is a good bit shorter than I, and the mirror occasionally
gets 'readjusted'. Once when I 'flipped' to nighttime dim, I noticed
that the brights were diverted DOWNWARDS instead of UPWARDS. I THINK
that this is evidence for the multiple reflection theory (but does
not negate the front surface effect at all. They BOTH seem to be
operating)

Check it OUT!



At  7:24 PM -0500  on  4/9/02,  KATHY DANIEL   wrote
> As I understand it, and according to Hewitt, the major reflection in
> the daytime
> is from the back surface of the mirror.  At night when the mirror is
> tilted, the
> back surface reflection goes over the driver's head and the driver sees the
> secondary reflection of the lights behind him/her from the front
> surface of the
> glass wedge.  This make a nice test question, complete with diagram for my
> reflection unit.
>
> Kathy Daniel
> Oakland High School
> Murfreesboro, TN  37130
>
> "Daniel L. MacIsaac" wrote:
>
> >  ...I frequently get odd requests from web-surfers who stumble across PHYS-L
> >  and its archives.  Yesterday I got a request from a surfer who was
> > looking for
> >  a nice explanation of the optics of a standard rear-view automobile mirror,
> >  which when tilted significantly dims the reflected image.
> >
> >  I think I know how the mirror works; I THINK it's a glass wedge and by
> >  controlling the incident angles one can reflect light multiple times
> >  within the wedge, attenuating it.  I could easily be very wrong.
> > But I can't
> >  find a simple explanation of the design on the web anywheres.  Can anyone
> >  help steer me to an appropriate online explanation?
> >
> >  Thanks in advance,
> >
> >  Dan M
> >
> >  Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
>  > danmac@nau.edu          http://purcell.phy.nau.edu         PHYS-L
> list owner

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Chuck Britton                                   Education is what is left when
britton@ncssm.edu                               you have forgotten everything
North Carolina School of Science & Math         you learned in school.
(919) 286-3366  x224                            Albert Einstein,        1936