#ITeachPhysics

Teaching "light as a wave" this week reminded me that most diagrams of electromagnetic (EM) waves use red & blue to distinguish between the electric & magnetic waves.

However, a quick search reveals whether the electric wave is red or blue (and hence the mag wave is the other colour) confirms there's disagreement. So, clearly ๐Ÿ˜€, an important question for #PhysicsFriday is:

By which colour do you think the electric wave should be represented?

#Physics

Red
36.4%
Blue
63.6%
Poll ended at .
The people have spoken, electric fields are blue.
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@MichaelPorter I get "Video not available".
ICEHOUSE - Electric Blue

Official music video for 'Electric Blue' taken from WHITE HEAT: 30 HITS out now! (c) Diva Records Pty Ltd

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@MichaelPorter Second time's the charm! ๐Ÿ˜€

Great song. Great band. Great Australian music.

@level98 From undergrad e&m with Kian Dy: โ€œElectric fields are red.โ€
@heafnerj There's nothing like being definitive! ๐Ÿ˜€
@level98 Heโ€™s Korean and I can still hear his voice as I write this.
@level98 Of course, if one is colorblind then it doesnโ€™t matter since color doesnโ€™t really exist anyway. ๐ŸŽจ

@heafnerj It's a really important point for teaching, textbooks etc.

Although (as you know) color-blind (or the correct spelling, colour-blind ๐Ÿ˜‰ ) generally doesn't mean one can't distinguish colours at all, but means certain colours are difficult to distinguish.

There are websites that provide advice on the most effective colour palettes to use so color-blind people can distinguish the colours but given there are many forms of color-blindness.

1/2

@heafnerj IMO one of the best things to do is ensure that colour is not the only distinguishing factor in any diagram etc.

E.g. make the electric field vectors dashed lines, and the mag field vectors solid.

A good strategy (that covers a range of possibilities e.g. someone printing in black and white) can be to assume any teaching material is to be presented in black and white, and then add colour simply as an additional feature for those who are able to use it. 2/2

@level98 The solid/dashed idea is brilliant. I donโ€™t think I ever saw that in a textbook.

@heafnerj I've seen it used in an exam question, which had to use it (because the exam was printed in black and white), so I can't claim the idea as my own. But while I don't specifically remember seeing it in a textbook, it's also possible/likely there is one that has used it.

I think the idea of always initially designing for black and white, is key.

@level98 @heafnerj When Iโ€™ve got the time during diagram creation, I give different vector quantities different arrowhead styles and ideally different line weights, as well as the color or greyscale differences.

โ€œDashedโ€ is nice but not always practical. If the arrows are sometimes very short, dashing them doesnโ€™t work well. X/dot arrows normal to the page are not really dashable either.

@sstoneb @level98 Arnold Arons was an advocate of using different arrowheads.
@heafnerj @level98 Ohh Iโ€™m in good company then!
@sstoneb @heafnerj Yes. Solutions for distinguishing various features need to fit the circumstance / diagram.
@level98 Of course. (I was attempting sarcasm but failed.)
@level98 "Other". Specifically, well labelled axes, then the can both be black. Saves a fortune in animation cycles. But beyond that, any two contrasting colours, standardising them can only lead to misconceptions (red/blue is high school magnetic poles, red black is DC +/-)
Normalise ignoring the colours and looking at the graph. Or just pick two random colours.
@level98 Althou I hadn't seen your colour blindness argument when I replied. Yeah, random colours doesn't work. Random pair of suitably high colour/contrast pairs?
@_thegeoff Yes. This is really a jokey poll based on what most people do. My response is: design for black and white (as mentioned/discussed in my other posts) add colour afterward... but like you say, check what else is out there / commonly used and try not to, at least, confuse with your choice of colour.
@_thegeoff With the important additional point (see other posts) of getting the relative orientation of the E and B fields correct!