InterviewSolution
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InterviewSolution
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The luminous dials of watches are usually made by mixing a zinc sulphide phosphor with an `alpha`-particles emitter. The mass of radium (mass number `226,half-life 1620 years`)that is needed to produce an average of `10` alpha`-particles per second for this purpose isA. `2.77 mg`B. `2.77 g`C. `2.77 xx10^(-23)g`D. `2.77 xx10^(-13)kg` |
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Answer» Correct Answer - d `|(dN)/(dt)|=lambdaN` number of radium nuceli in `m g =(N_(A)m)/(226)` Decay constant, `lambda =(0.693)/(t_(1//2)) =(0.693)/(1620 xx 3.16 xx10^(7))` `|(dN)/(dt)|=10=(0.693 xx 10^(23)m)/(226) xx (0.693)/(1620 xx 3.16 xx10^(7))` `:. m=(10 xx 226xx1620 xx 3.16 xx10^(7))/(6.02 xx 10^(23) xx0.693)` `=2.77 xx 10^(-10) g` `=2.77 xx 10^(-13) kg`. |
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