Determine the amount of `""_(84)Po^(210)` (polonium ) necessary to provide a source of `alpha ` -particles of 5 millicurice strength , if life of polonium is 138 days (given ,1 curie `=3.7xx10^(10)` disintegrations /s )

Explanation

from the relation ,`R=lamda N,` we have
`N =( R)/(lamda)` ( here ,R = activity of sample )
where ,` R =5xx10^(-3)x3.7xx10^(10) dps`
`t_(1//2)= 138 days = 138 xx24xx3600 s`
`therefore N=((5xx10^(-3))(3.7xx10^(10)))/((0.693//138xx24xx3600)) ( :' lamda (0.693)/(t_(1//2))`
number of moles `xx` given mass `=(2.28xx10^(-9))(210)g `
`=1.11xx10^(-6)g`