quiz1spr2000 - .~ , . '. ENGSC 3313, Spring 2000 .nswer...

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, . '... 4 Name ENGSC 3313, Spring 2000 Quizl .nswer any 4 Questions only, 1 point each 1 .An important radioactive isotope is strontium-90 because it is absorbed by bone (The Sr substitutes for Ca in Ca3(PO4)V. It has a half life of 30 years. What proportion would have decayed after 20 years? We have exponential decay Substituting 0.5 = e-30/A and A = 43.5 years Repeating Hence, proportion decayed is 1- 0.63 = m Studies indicate that the intensity of green light decays exponentially as it passes through sea water. The intensity at 1.0 meter below the surface is one quarter of the surface intensity .At what depth is the intensity one tenth of the surface intensity? 2 I = Ioe- 11 x At x = 1.0 m, :=- = 0.25 I In(0.25) = -Jl (1.0 m) => Jl= 1.386 m" In(O.l) = (-1.386) x ~ x = 1.66 m A metre is defined as 1,650,763.73 of the wavelength of the photon emitted when ~ electron in Kr86 goes from the 5d to 2p orbital. Please calculate the energy of this transition in e V. Planck's constant is 0.662 x 10-33 Js. The velocity of light is 0.299 x 109 m/s and leV= 0.160 x 10-18 J. 3
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quiz1spr2000 - .~ , . '. ENGSC 3313, Spring 2000 .nswer...

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