Does lead absorbs all kind of radiation?

Answer 1

No shielding material truly absorbs electromagnetic radiation, it attenuates it. The attenuation is by a certain amount for a certain standard thickness. The standard thickness is called the half thickness and is used to quantify shielding effectiveness for a given type of electromagnetic radiation. One half thickness attenuates the power of the given type of radiation by 50% or in decibel units -3dB. Thus the power of the radiation after a given number of half thicknesses of a given shield is:

1. 50% or -3dB
2. 25% or -6dB
3. 12.5% or -9dB
4. 6.25% or -12dB
5. 3.125% or -15dB
6. 1.5625% or -18dB
7. 0.78125% or -21dB
8. 0.390625% or -24dB
9. 0.1953125% or -27dB
10. 0.097655625 or -30dB
11. etc.

As you can see no thickness of shield material can completely attenuate electromagnetic radiation to nothing, also the higher the frequency of electromagnetic radiation the longer the half thickness is so for x-rays and gamma rays it takes very large thicknesses to get any useful attenuation.

For particle radiation the situation is completely different, the radiation can sometimes be absorbed and sometimes can't:

1. alpha particles are 100% absorbed by a single sheet of paper or the first layer of living tissue they encounter
2. most beta particles are 100% absorbed by a single sheet of thin metal foil (e.g. aluminum foil)
3. neutrons penetrate most matter as if it was not there, unless it contains certain elements (e.g. boron, cadmium, uranium) that have high neutron capture crosssections in which case the neutron flux is attenuated much like electromagnetic radiation as described above
4. neutrinos penetrate all matter as if it was not there
5. etc.