>A summer holiday question for those who are suffering from lack of PTNC
>contact:
>
>Are microwaves
>
>a) a distinct grouping in the em spectrum as in radiowaves, microwaves,infra
>red, visible, etc. ?
>
>or b) A subset of radio waves as in long wave, medium wave, short wave,
>microwave ?
>
>Just curious to know.
>
>Martyn Williams
>

Surely Martyn knows that we are all relativists and constructivists
in science education these days. Microwaves can be whatever we decide
we want them to be - or at least whatever the outcome of the
socio-political process (called science) may temporarily class them
to be in accordance to the current cultural zeitgeist.

And with my tongue now removed from my cheek (for the silly season is
rapidly coming to a close), the serious point.

One view of what science does is observe regularities in nature and
create ways of describing those patterns by constructing categories
and concepts for (a) organizing sense (and professionally obtained)
data and so (b) making predictions allowing us to act in the world in
'meaningful' ways.

Now the question of the extent to which our constructed categories
map onto any kind of underlying reality is of course one way of
keeping philosophers in business. However, I would suggest that a
common-sense viewpoint would be that some of our categories map onto
the world in cleaner ways that others.

So, the category 'electron' is a human construct that seems to map
pretty closely onto a fundamental regularity in nature.
The category 'acid' is a much more fluid [sic] mapping (with
historical changes in what the category should include, which are
reflected in what we expect from students at different levels).
The category mammal seems even more arbitrary (especially when
considering the fossil record) although that is not to suggest there
are not patterns in the evidence, just that useful category
boundaries can not be established as readily as with 'electron'.

I would think that the concept e-m radiation maps quite well onto a
pattern in the data we observe in nature. The category visible light
is obviously closely tied to the instrumentation used to collect data
(human eyes) and there is no obvious categorical shift in the
properties of near IR, visible and near UV apart from their
detectability by human eyesight. The distinction between X-rays and
gamma-rays is made in terms of origins which is why these 'regions'
of e-m spectrum overlap. I am not aware of any way of distinguishing
between e-m radiation from the overlap region if its origin was
unknown - and I don't know if there is a standard convention here -
label as X-ray unless known to be a gamma-ray? - presumably we just
have e-m radiation of certain characteristics and properties that are
completely independent of their origins. (But do not assume your
students would 'naturally' realize this: many students think that
electrons will want to return to their own atoms, as if a sodium
electron had some kind of marker or memory.)

So perhaps Martyn's question should be

>Are microwaves [currently/best considered to be/defined as]
>
>a) a distinct grouping in the em spectrum as in radiowaves, microwaves,infra
>red, visible, etc. ?
>
>or b) A subset of radio waves as in long wave, medium wave, short wave,
>microwave ?

Keith






--


Dr. Keith S. Taber
http://www.educ.cam.ac.uk/staff/taber.html
University Lecturer in Education
University of Cambridge Faculty of Education
Homerton College site
Hills Road
Cambridge CB2 2PH


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