On 20/05/16 14:13, Chris Hogg wrote:
On Fri, 20 May 2016 11:23:09 +0100, Tim Streater
wrote:

In article , The Natural Philosopher
wrote:

On 19/05/16 19:37, Tim Streater wrote:
In article , Chris Hogg
wrote:

I thought it was complete ******** too; it treats microwaves as if
they're tennis balls, but I'm no microwave expert. If it's not
********, and if microwaves can't leak out of a hole smaller than 12
cm. why all the fuss in the past about microwaves leaking around
ill-fitting doors, and why the need for a fine mesh across the window
in the door? If the article is OK, you barely need to shut the door,
let alone worry about leaks around the edge, and wide-mesh netting
would do in the window allowing a much better view of the contents.
What am I not understanding?

This issue is nothing specifically to do with microwaves. It relates to
*all* sorts of waves and their behaviour. Look up diffraction. I'd do
it meself, but SWMBO has just announced that the scoff is ready.

The issue us not diffraction, but reflection.

Chris was asking why you couldn't just use wide-mesh netting. I'm
saying that considerable energy can diffract through that (apparently),
even if the mesh size is less than the wavelength.


If considerable energy can diffract or otherwise pass through wide
mesh netting, and I don't doubt it for a minute, how can a bloody
great hole 12cm across not be a major hazard, as the article linked to
at the top of this thread said wasn't? (hope I've not got double
negatives there, but YSWIM!)

well 2GHZ is around 3.75cm for a quarter wave..

so its of the order of a wavelength anyway.

I am fairly sure that diffraction is a bit of a red herring though.

Its one of those lectures I probably didnt pay much attention to, but I
think its a matter of reflection.

You can build a radar reflector adequately out of chicken wire..


--
"It is an established fact to 97% confidence limits that left wing
conspirators see right wing conspiracies everywhere"