(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The intensity of a collimated, parallel beam of K atoms is reduced 3.0% by a layer of Ar gas 1.0 mm thick at a pressure of 6.0 x 10^-4 mmHg. Calculate the effective target area per argon atom. (this is B-4 from "introductory exercises in physics")

2. Relevant equations

I've been trying transmission T = I/I naught = e^(-x/l)

Where x is 1mm, T is .97, and l is the mean free path which includes the cross section.

3. The attempt at a solution

Im assuming the cross section of argon is the same thing as the effective target area per argon atom they are asking for, so I solve for that. I use l = {(2^.5) A n}^-1. A is the area im looking for and n is the number of molecules per volume. To get n I convert the pressure given into molecules/volume. Not sure why but I cant seem to get anything close to the stated answer of 1.4 x 10^-14 cm^2.

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# Homework Help: Target area, collimated beam

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