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X-Rays. Help Me To Solve This Question.?
If a beam of X-rays is incident upon material that has an absorption coefficient of 200 cm^-1, what thickness is necessary to reduce the number of emerging x-ray photons to one-half of the number of incident photons?
1 Answer
- 1 decade agoFavorite Answer
Io=100%=1
I(t)=50%=.5
u=200/cm
t=?
Attenuation of particles or photons follow the exponential formula below.
I(t)=Io X e^(-u*t) (1)
where t is the distance traveled, Io is the intensity of the original beam, and u is your mediums macroscopic cross section, which is the summation of all relevant cross sections. Normally for a photon this includes compton scattering, absorption, and pair production if the energies are high enough.
simplify equation 1 to the below equation
t=- LN( I(t) / Io )/ u (2)
plugging all knows into equation 2 gives
t= -LN(.5)/200 cm = .00347cm
t= .00347cm
