b) An electronic device operating at 100MHz is to be installed in a shielded enclosure made of an annealed copper. The conductivity and relative permeability of the shield material are 5.82107S/m and 1 , respectively. For a perfectly shielded enclosure, determine the following: (i) The thickness of the shield to provide an absorption loss of 90dB. [3 marks] [Hint: =2,0=4107H/m,0=8.8541012F/m ] (ii) The reflection loss and the shielding effectiveness of this enclosure in dB, assuming that multiple reflection loss is negligible. [Hint: R=20log(30)dB ] [3 marks] (iii) A stainless steel with a relative conductivity of 0.01 and relative permeability of 200 is used as the material for the shielded enclosure. By using the same thickness of annealed copper shield in (b)(i), calculate the absorption loss, reflection loss and the shielding effectiveness of this stainless steel material. [5 marks] (iv) Conclude your observation about the shielding effectiveness for both materials