# Structure.questions_IV_answer - MTLE-2100 Structure of...

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MTLE-2100 Structure of Engineering Materials, Questions IV-answers 1. Low energy x-ray is used for radiology. Using the absorption data at λ = 1.542 Å estimate the ratio in the transmitted x-ray intensity of flesh and bone. The flesh consists mainly of C, H and O but assume it is mainly H 2 O with density 1.0 g/cm 3 and thickness of 10 cm. The bone is mainly hydroxyapatite, Ca 5 (PO 4 ) 3 (OH) and assume its density is 2 g/cm 3 and thickness is 2 cm. Use the data in appendix 8. Bone: Molecular weight 5x40 +3x31+13x16+1= 502 Weigt fraction Ca: 200/502=0.398; P:93/502=0.185; O:208/502=0.414; H:1/502=0.002 μ / ρ = 0.398x171.4+0.185x77.28 + 0.414x11.03 + 0.002x 0.3912=68.2+14.3+4.6+0=87.1 I =I 0 exp (-87.1x2x2) = 4.5xE-152 Flesh: H 2 O molecular weight 18 Weight fraction O:16/18 =0.889; H:2/18 =0.111 μ / ρ = 0.889x11.03 + 0.111x0.3912 = 9.806 + 0.0434=9.849 I =I 0 exp (- 9.849x1x10) =1.7E-43 Transmission ratio of Flesh/Bone = 1.7E-43/4.5E-152 = 3.7E108 2. Television uses a high voltage (assume, 10,000V) electron beam which can generate x-ray. TV viewers are protected by glass CRT (Cathode ray tube). Glasses can contain SiO 2 , CaO, Al 2 O 3 , MgO, Na 2 O, K 2 O, SrO, BaO, PbO. Which components are effective to protect TV viewers? First, calculate the shortest wavelength limit and then check the absorption coefficient at that wavelength. λ

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