Re: [Phys-L] Inverse Square for reflected light

[Shahram Mostarshed <smostarshed@gmail.com>]

How close to the mirror was the measurements? Isn't this consistent with
electric field strengths near a flat screen (constant)?

Shahram M.
Physics Instructor, Stanford OHS


On Wed, Dec 8, 2021 at 8:35 AM Scott Goelzer via Phys-l <
phys-l@mail.phys-l.org> wrote:

> I wanted some opinions or confirmation about some results of an optics
> experiment some of our freshman devised.
>
> In the first part, students were tasked with proving the inverse square
> lab using a Pasco light meter and a standard ray box. No problems -
> reasonable and expected results were obtained by varying the distance.
>
> Student were then asked to devise their own experiments to test inverse
> square law. Two groups decided to measure the intensity of reflected light
> from a plane mirror as a function of distance. They were puzzled (as was
> their teacher) with very linear results. At this time, I believe the groups
> did a reasonable job taking measurements.
>
> There is surprisingly little about this effect on any physics site, but
> some photography sites confirm the effect without explanation.
>
> Best explanation I could give was that the mirror was not functioning as a
> point source any longer and was producing effectively parallel wave fronts.
>
> Any ideas?
>
> Scott
>
>
>
>
>
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