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Natural radioactivity is a spontaneous and self disruptive activity exhibated by a number of heavy elements in nature. Thus a heavy element disintegrates by itself without being forced by any external agent to do so. According to radioactive decay law, the number of atoms disintegrated per second (i.e., rate of disintegration of radioactive atoms) at any instant is directly propotional to the number of radioactive atoms actually in the sample at that instant, i.e., -(dN)/(dt) propN or R=-(dN)/(dt)=lambdaN, where lambda is decay constant. Read the above passage and answer the following questions: (i) The count rate form a radioactive sample containing 10^(16) atoms is 4xx10^(6) per second. What is the value of decay constant? (ii) Name the three types of radiactive radiations. Which one of them is most penetrating? (iii) What does radioactive decay law imply in day to day life? |
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Answer» Solution :(i) Here, `N=10^(16) and (dN)/(dt)=4xx10^(6)per sec. lambda=?` FORM `(dN)/(dt)=lambdaN` `lambda=(dN//dt)/N=(4xx10^(6))/(10^(16))=4xx10^(-10)sec^(-1)` (ii) The three types of radiactive radiations are : `alpha`-rays , `beta`-raysand `gamma`-rays. Out of then, `gamma`-rays have MAXIMUM penetrating power. (iii) Radioactive decay LAW is the law of mass action, i.e., larger the available mass, greater is its rate of decay. The same applies in day to day LIFE. Larger the population, greater is their decay rate, i.e., under GIVEN conditions, when number of people is large, the rate at which they the die is also large. The reverse is also true. |
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