Atomic weight of a radioactive element is `M_(W)` gm. Radioactivity of m gm of its mass is :-
(`N_(A) = ` Avogardro number, `lambda` = decay constant)

The beta - decay of a radioactive element results in formation of its :

The average life of a radioactive element is ............. of the decay constant.

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 activity of a radioactive elements (decay constant lambda ) becomes (1)/(3) of initial activity A_(0) in 9 years then the decay constant after 9 years will :

The decay constant of a radio active element, which disintergrates to 10 gms from 20 gms in 10 minutes is

If N_0 = Number of radioactive nuclei present at t -= 0, N = Number of radioactive nuclei present at time t = t and lambda is the decay constant, then the radioactive decy equation is

If m g of a radioactive species (molar mass M) has decay constant lambda The specis activity of sample at t = is given by: