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4hv.org :: Forums :: General Science and Electronics
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Patrick
Fri May 05 2017, 10:50AM
Patrick Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Ok simple question.

I see online, and as I was taught that the area of a rectangle is L x W. So 2 x 3 cm should be 6 cm^2 right ?

But I keep seeing 6 cm^-2 ? all over these scientific and technical PDFs Im reading. I dont get it. Why is that negative there !?

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Dr. Slack
Fri May 05 2017, 10:57AM
Dr. Slack Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
so post a link to one of these scientific and technical pdfs and let's see the context, my all-seeing-eye can't quite read over your shoulder.

It's correct to use a length exponent of -2, or per area, if what's being reported is 'something per area', like pressure as N/m^2, also written as N.m^-2. Note the change of sign of exponent, and the change between divide and product.
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Patrick
Fri May 05 2017, 11:04AM
Patrick Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
here:

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hen918
Fri May 05 2017, 12:10PM
hen918 Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
Yep, Dr slack is correct. another way to write those units is: mW/cm^2.
If you remember your math(s), taking a minus power is the same as the reciprocal (putting 1 over it) to the power without the minus.
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