Question

Question:   Scientists also use x-ray generators to produce x-rays used to study the structure of proteins and other biological molecules. Two types of anode materials are commonly used in this sort of experiment, and only the characteristic x-rays emitted ordinarily are used. For copper anodes, the characteristic radiation most frequently used is 8.0 keV, and for molybdenum anodes 17.4 keV is used. Aluminum (Z = 13) works well for shielding when the copper anode is used, but scientists must be careful to switch to steel or brass shielding when molybdenum anodes are used. Explain why, using information from the following table.

Shielding metal-Aluminium ,Z Value 13,Density 2.8g/cm^3

Shielding metal-Steel,Z Value (Largely iron with Z =25),Density 8g/cm^3

Shielding metal-Brass,Z Value(Alloy of copper with Z=29, and zinc Z=30, Density 8.5g/cm^3

Could you please explain clearly ,thankyou very much

Answer 1

When copper anode is used the energy of x ray is less hence we can use a lesser dense material as shielding hence aluminium being less dense as well as cheaper and highly abundant metal can be use here.

But when more energetic xray is used such as one produced from molybdenum denser material is required to stop radiation. Hence we use alloys like brass or steel or sometime lead. Here higher Z value also plays vital role. Higher the z value higher will be the absorbing power of metal.