Particles and their anti-particles have
A. The same masses but opposite spins
B. The same masses but opposite magnetic moments
C. The same masses and same magnetic moments
D. Opposite spins and some magnetic moments
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 :
A. 40
B. 25
C. 15
D. 10
In Sun, the important source of energy is
A. proton-proton cycle
B. carbon-nitrogen cycle
C. carbon-carbon cycle
D. nitrogen-nitrogen cycle
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 :
A. 1 : 2 : 4
B. 1 : √2 : 1
C. 2 : √2 : 1
D. 1 : 1 : 2
A free neutron decays spontaneously into :
A. a proton, an electron and anti-neutrino
B. a proton, an electron and a-neutrino
C. a proton and electron
D. a proton, and electron, a neutrino and an anti-neutrino
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
A. Xt1 - Yt2
B. X-Y
C. X-Y / г
D. (X -Y) г
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)
A. 4.23x109
B. 3.16x1010
C. 3.61x1010
D. 2.16x1010
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)
A. 6 x 1018
B. 6 x 1017
C. 1017
D. 6 x 1016