The plot of the number (N) of decayed atoms versus activity (R) of a radioactive substance is

99% quantity of a radioactive substance decays between

The graph between number of decayed atoms N' of a radioactive element and time t is.

Half-life of a radioactive substance is T. At time t_1 activity of a radioactive substance is R_1 and at time t_2 it is R_2 . Find the number of nuclei decayed in this interval of time.

Half-life of a radioactive substance is T. At time t_1 activity of a radioactive substance is R_1 and at time t_2 it is R_2 . Find the number of nuclei decayed in this interval of time.

The initial number of radioactive atoms in a radioactive sample is N_0 . If after time t the number of becomes N, then N=N_0e^(-lambdat) , where lambda is known as the decay constant of the element. The time in which the number of radioactive atoms becomes half of its initial number is called the half-life (T) of the element. The time in which the number of atoms falls to 1/e times of its initial number is the mean life (tau) of the element. The product lambdaN is the activity (A) of the radioactive sample when the number of atoms is N. The SI unit of activity is bequerel (Bq)' where 1 Bq = 1 decay. s^(-1) , and Avogadro's number, N=6.023xx10^23 What is the ratio of activity of same amount of sodium-24 to that of iodine-131? [half life of sodium-24 is 15h.] (A) 1/70 (B) 1/7 (C) 7 (D) 70

The initial number of radioactive atoms in a radioactive sample is N_0 . If after time t the number of becomes N, then N=N_0e^(-lambdat) , where lambda is known as the decay constant of the element. The time in which the number of radioactive atoms becomes half of its initial number is called the half-life (T) of the element. The time in which the number of atoms falls to 1/e times of its initial number is the mean life (tau) of the element. The product lambdaN is the activity (A) of the radioactive sample when the number of atoms is N. The SI unit of activity is bequerel (Bq)' where 1 Bq = 1 decay. s^(-1) , The half-life of Iodine-131 is 8d. Its decay constant (in SI) is - (A) 10^(-6) (B) 1.45xx10^(-6) (C) 2xx10^(-6) (D) 2.9xx10^(-6)

The initial number of radioactive atoms in a radioactive sample is N_0 . If after time t the number of becomes N, then N=N_0e^(-lambdat) , where lambda is known as the decay constant of the element. The time in which the number of radioactive atoms becomes half of its initial number is called the half-life (T) of the element. The time in which the number of atoms falls to 1/e times of its initial number is the mean life (tau) of the element. The product lambdaN is the activity (A) of the radioactive sample when the number of atoms is N. The SI unit of activity is bequerel (Bq)' where 1 Bq= 1 decay. s^(-1) . After how many days the activity of Iodine-131 will be 1/16 th of its initial value. [The half-life of Iodine-131 is 8 d.] (A) 24 d (B) 32 d (C) 40 d (D) 48 d

The initial number of radioactive atoms in a radioactive sample is N_0 . If after time t the number of becomes N, then N=N_0e^(-lambdat) , where lambda is known as the decay constant of the element. The time in which the number of radioactive atoms becomes half of its initial number is called the half-life (T) of the element. The time in which the number of atoms falls to 1/e times of its initial number is the mean life (tau) of the element. The product lambdaN is the activity (A) of the radioactive sample when the number of atoms is N. The SI unit of activity is bequerel (Bq)' where 1 Bq = 1 decay. s^(-1) . The half-life of Iodine-131 is 8 d. What is the activity (in Bq) of 1 g of Iodine? (A) 2.3xx10^15 (B) 4.6xx10^15 (C) 6.9xx10^15 (D) 9.2xx10^15

State the law of radioactive decay and deduce an expression for half life of a radioactive substance.