So pho ton ma nguon phat ra trong mot s la $n=\frac{P.\lambda }{hc}$
So photon nay se trai deu tren mat cau co ban kinh la R chinh la khoang cach to nguon toi mat
Mat do photon tren mot don vi dien tich mat cau la
$m=\frac{n}{4\pi R^{2}}$
De van con nhin thay anh sang thi so photon lot vao con nguoi la
$N=m.\pi .r^{2}=80$ voi $r$ la ban kinh con nguoi
Con lai la thay so tinh $R$ dap so la 274km
Neu dap so co lech thi lam tron nha
Cach lam nhin chung la the chac ban cung chi can cach lam thoi