The half life of Ra226 is 1620 years. Then the number of atoms decay in one second in 1 gm of radium (Avogadro number = 6.023x1023)
4.23x109
3.16x1010
3.61x1010
2.16x1010
A radioactive sample has half life of 5 days. To decay from 8 micro-curies to 1 micro-curie, the number of days taken will be :
40
25
15
10
A proton, a deuteron (nucleus of 1H2) and an α-particle with same kinetic energy enter a region of uniform magnetic field moving at right angles to the field. The ratio of the radii of their circular paths is :
1 : 2 : 4
1 : √2 : 1
2 : √2 : 1
1 : 1 : 2
Particles and their anti-particles have
The same masses but opposite spins
The same masses but opposite magnetic moments
The same masses and same magnetic moments
Opposite spins and some magnetic moments
To generate power of 3.2 MW, the number of fissions of U235 per minute is : (Energy released per fission =200 MeV; 1eV=1.6x10-19J)
6 x 1018
6 x 1017
1017
6 x 1016
The radioactivity of a sample is 'X' at a time 't1' and ‘Y’ at a time 't2'. If the mean life time of the specimen is г the number of atoms that have disintegrated in the time interval (t1 – t2) is
Xt1 - Yt2
X-Y
X-Y / г
(X -Y) г
In Sun, the important source of energy is
proton-proton cycle
carbon-nitrogen cycle
carbon-carbon cycle
nitrogen-nitrogen cycle
A free neutron decays spontaneously into :
a proton, an electron and anti-neutrino
a proton, an electron and a-neutrino
a proton and electron
a proton, and electron, a neutrino and an anti-neutrino