A radioactive substance has a half life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be
(1) 12.5%
(2) 87.5%
(3) 8.5%
(4) 25.1%
An element used for radioactive carbon dating for more than 5600 years is
(1) C-14
(2) U-234
(3) U-238
(4) Po-94
N atoms of a radioactive element emit n alpha particles per second. The half life of the element is
(1) nN sec
(2) Nn sec
(3) 0.693 Nn sec
(4) 0.693 nN sec
The radioactive nucleus N137 decays to C136 through the emission of
(1) Neutron
(2) Proton
(3) Electron
(4) Positron
The radioactive decay of uranium into thorium is expressed by the equation U23892→Th23490+X where 'X' is
(1) An electron
(2) A proton
(3) A deuteron
(4) An alpha particle
In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process
(1) Proton
(2) Neutron
(3) Electron
(4) Photon
The half life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be
(1) 93.75%
(2) 75%
(3) 25%
(4) 6.25%
In the uranium radioactive series, the initial nucleus is U23892 and the final nucleus is Pb20682. When the uranium nucleus decays to lead, the number of α-particles emitted will be
(1) 1
(2) 2
(3) 4
(4) 8
Which of the following is a correct statement
(1) Beta rays are same as cathode rays
(2) Gamma rays are high energy neutrons
(3) Alpha particles are singly ionized helium atoms
(4) Protons and neutrons have exactly the same mass
The half life of I131 is 8 days. Given a sample of I131 at time t = 0, we can assert that
(1) No nucleus will decay before t = 4 days
(2) No nucleus will decay before t = 8 days
(3) All nuclei will decay before t = 16 days
(4) A given nucleus may decay at any time after t = 0