Re: magnetic lens and em lab

[palmer@sfu.ca (Leigh Palmer)]

> Where I can find a text for e.m. lab?, with electron optics lab?,
> I am interested to demo a magnetic lens for my students.

I just want to share a relevant anecdote. In 1962, while I was a
graduate student at Cal, we visited the World's fair in Seattle.
I had never before in my life seen an electron microscope, and
there was one being demonstrated in, I think, the GE pavilion.
I was thrilled! The attractive young lady operating the
microscope showed me various things she could do with it and of
course I was dazzled. She answered a couple of my questions
reasonably competently and finally, thinking that she must know
a lot that I didn't, I asked her "Why does the image rotate like
that when you change the magnification?" She looked at me and
patronized me with "Of course it *always* does that." It was
only after I returned to Berkeley that was able to get at a book
which explained electron optics to me.

I would suggest that you take your students to visit an electron
microscope if that is possible. You could supplement that
experience with a standard undergraduate laboratory e/m exercise.
Another possibility is to take a TV set and manipulate the
deflection yoke - but be sure you protect yourself and your
students from coming into contact with the high voltage, and
even with the high voltage parts when the set is turned off. The
CRT will retain a painful wallop of stored energy.

If you get ambitious, try wrapping a coil around the CRT between
the deflection yoke and the screen. (I'm thinking of using a
black and white TV, incidentally). This should be capable of
rotating the picture when a current is passed through it.

Leigh