Re: [Phys-l] "Unlearning"

[Scott Orshan <sdorshan@aol.com>]

 My "favorite" piece of false information that is regularly taught in 
physics classes is that color equals wavelength, and that wavelengths 
can be combined through Additive Color Mixing - that Red+Green makes 
Yellow, Blue+Green makes Cyan, etc., like on a TV screen.

This is in no way related to Physics - if you look at the wavelengths 
involved, it wouldn't work out, even in a non-linear medium.

This is all about Biology. And not just general biology, Human biology. 
Unlike the ear, which can pick out thousands of individual frequencies 
and combinations of these frequencies (such as musical chords and more 
complex sounds like voices), the retina only responds to three main 
bands of wavelength, and produces color through a complex and not 
completely understood interaction over the entire visual field. (What 
wavelength is Silver? How about Pink? Brown? - see color is not just 
about wavelength).

As far as physics is concerned, Red plus Green simply makes Red plus 
Green. EM radiation of multiple wavelengths can pass through the same 
space and remain distinct (otherwise we'd have only one radio station to 
listen to). Most objects that look Yellow are actually reflecting Red 
and Green. Color Addition does not belong in physics books! It is 
cognitively at odds with other basic information that has been taught.

As far as refraction goes, it makes no sense to describe a light wave as 
having a width, where you can grab one end and slow it down, while the 
other end rotates around as if it were a stick. We could simply use the 
shortest time of travel, or just teach it through simple observation and 
measurement, and then give Snell's law to quantify the relationship 
without a real explanation.

    Scott

On 9/10/2010 12:00 PM, phys-l-request@carnot.physics.buffalo.edu wrote:
>   ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 09 Sep 2010 18:45:08 -0400
> From: "Ann Reagan"<areagan@csmd.edu>
> Subject: Re: [Phys-l] "Unlearning"
> To:<phys-l@carnot.physics.buffalo.edu>
> Message-ID:<4C892B340200004C00008AF0@webacc1.csmd.edu>
> Content-Type: text/plain; charset=US-ASCII
>
> Re: Comment: "Why do HS teachers insist on teaching what must be unlearned?"
>
> You mean, why teach things we all KNOW are wrong, like F = ma or P = mv? Or why teach that thermal expansion is linear , or that air obeys the ideal gas law? Perhaps because in a wide range of important cases, it gives a useful working approximation that describes the world in which we live.
>
> Dr. Ann M. Reagan
> Adjunct Faculty
> Department of Math/Physics/Engineering
> College of Southern Maryland, Leonardtown Campus