Spring17 REIFENBERGERI Activities and Due Dates I HW Electric Fields /20/2017090

Question

Spring17 REIFENBERGERI Activities and Due Dates I HW Electric Fields /20/20170900 AM 61.8/100 G 1/5/2017 o530 PM Print calculator s Periodic Table estion 3 of 19 Sapling Learning A physicist developed a device that generates a beam of alpha particles (each which is a helium nucleus, consisting of two protons, two neutrons, and no The device ejects a stream of 4.40 x10 per second. You are testing different shielding materials for a test chamber that will house the alpha particle generator. You prepare a sheet of one potential material in an electrically neutral state, mount it on a perfectly insulating stand, and fire the alpha particle device at it for 12.3 seconds. Afterward, you measure that the charge of the sheet is 1.94 x 105 coulombs, Assume that none of the alpha particles bounced back from the sheet, meaning that the alpha particles either were captured by the or through the shielding. What percentage of the alpha penetrated completely through the material? A O 2 Check Answer Next Exit Previous a

Explanation / Answer

no of alpha particles ejected per second = 4.40*103

time = 12.3 second

no of alpha particles arriving at the material , N0 = 4.40*103 *12.3 = 54.12*103

no of alpha particles captured, Nc = charge accumulated / charge of aplha particles ( 2e)

Nc = 1.94*10-15 C / 2*1.6*10-19 C

Nc = 6.062 *103

No of alpha particles penetrated, Np = N0 - Nc

Np = 54.12*103 -  6.062 *103 = 48058

% of penetrated alpha particles =( Np / N0 )*100

= (48058 / 54.12*103 )*100

= 88.79%

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