Does the amount of radiation (cpm) change when shielding made from different material is used?

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The type of shielding used to block various kinds of radiation makes a huge difference depending on the type of radiation present.  There are three basic types of radiation: alpha, beta, and gamma.  Alpha radiation produces alpha particles.  This is a relatively weak radiation that can be blocked with a simple sheet of paper.  Beta radiation particles are stronger and will penetrate paper but can be stopped by a thin sheet of metal like aluminum.  Gamma radiation is not composed of particles but electromagnetic photons instead.  It is a much more powerful radiation and requires a lead barrier for effective shielding.  So you can see that the type of shielding used matters greatly on the type of radiation present.

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Does the amount of radiation (cpm) increase or decrease as thickness of the shielding increases while the distance between the source and the stays the same?

We are asked if the shield thickness makes a difference in the amount of radiation passing through if the distance is kept the same.  The answer is yes.  A thicker shielding has more mass and will therefore block more of the radiation.  Alpha and beta types of radiation emit actual particles.  The shielding actually deflects these particles and prevents them from travelling forward.  Once you have reached a certain thickness, all of the particles are blocked and any extra shielding really doesn't do anything more.  X-rays and gamma radiation, however, are photon base radiation and can therefore penetrate much deeper since there is no particle to block.  Shielding thickness makes a huge difference here.  More shielding provides more atoms to absorb this radiation and prevent it from passing through.

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