How to calculate the radiation at a certain distance from Japan?

I happen to know a man from California ( lets just say he's an idiot ) who is getting all freaked out about radiation reaching him from Japan's nuclear reactors. I was wondering how to calculate the level of radiation in southern california if the source is in Japan. ( what formula or equation?) I'm pretty sure the inverse-square law would work, but I never really used it much, so I'm kinda rusty. Then I can post it on facebook just to be a smart-*** and show him how ridiculous he's being.How to calculate the radiation at a certain distance from Japan?
yeah, the inverse square law is what you need, but you also need to know the amount of radiation produced at the plant (i have no clue, you'll have to find out online or something) and treat the plant itself as a point source of radiation, then divide that number by the distance from the plant to california squared (in metres) and you'll have the intensity of the radiation where you are. Dont worry, its MUCH too far to hurt north america at all. Even if the wind is pointing directly at us all the radioactive material will land in the pacific. We'll all be find.How to calculate the radiation at a certain distance from Japan?
According to wikipedia:

Distance: Radiation intensity decreases sharply with distance x, according to an inverse square law (in an absolute vacuum) .[3] practically i = Io e^(-ux)



Not sure how if we can simply take mSv/ meters squared?



From wikipedia again: I=P/4(pi)r^2

http://bit.ly/hlvCw0

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How to calculate the radiation at a certain distance from Japan?
DIRECT radiation? He must be joking!

The radiation is in particles thrown into the air, and blown along by winds. It will fall to ground in time, but could be carried almost anywhere before it does.

I think they assume that outside the exclusion zone they have in place, possible radiation dosage is within tolerable levels. Decontamination of clothing and skin, is the primary fix.