A radioactive sample decays by simultaneous emission of two particles having respective half-lives of 1,620 years and 810 years. After what time, one fourth of the sample will be left behind?

In the chemical analysis of a rock the mass ratio of two radioactive isotopes is found to be 100:1. The mean lives of the two isotopes are 4xx10^9 years and 2xx10^9 years, respectively. If it is assumed that at the time of formation the atoms of both the isotopes were in equal propotional, calculate the age of the rock. Ratio of the atomic weights of the two isotopes is 1.02:1.

There are two radioactive substances A and B. Decay constant of B is two times that of A. Initially both have equal numbr of nuclei. After n half lives of A, rate of disintegration of both are equal. Find the value of n.

A radioactive sample can decay by two different processes .The half-life for the first process is T_1 and that for the second process is T_2 . Show that the effective half-life T of the nucleus is given by 1/T=1/(T_1) + 1/(T_2) .

Starting from 10g of a radioactive element, 0.25 g was left after 5 years. Calculate The time required for half of the element to decay.

At any instant, the ratio of the amount of radioactive substance is 2:1. If their half lives be respectively 12 and 16 hours, then after two days what will be the ratio of the substances?

Two radioactive nuclides A and B have half-lives 50 min and 10 min respectively . A fresh sample contains the nuclides of B to be eight times that of A. How much time should elapse so that the mumber of nuclides of A becomes double of B ? a) 30 b) 40 c) 50 d) 100

The half-life of a radioactive substance is 1,672 years. If the initial mass of the substance is 1 g, after how many years will only 1 mg of it to be left behind?

Select the correct statement(s) : a) On bombarding ._(7)^(14)N nuclei with alpha -particle, the nuclei of the product formed after release of proton would be ._(8)^(17)O b) Decay constant does not depend upon temperature c) Nuclide and its decay product after alpha -emission are called isodiaphers d) Half-life of radium is 1580 years . Its average life will be 1097.22 years