Which of the following statements is true for nuclear forces?
They obey the inverse square law of distance.
They obey the inverse third power law of distance.
They are short range forces.
They are equal in strength to electromagnetic forces.
Heavy water is used as a moderator in a nuclear reactor. The function of the moderator is
to control energy released in the reactor
to absorb neutrons and stop chain reaction
to cool the reactor
to slow down the neutrons to thermal energies
Total binding energy f products formed due to nuclear fission is less than parent fissionable material
Mass of some particles is converted into energy
The mass density of a nucleus varies with mass number A as
A2
A
constant
1/A
A radioactive nucleus (initial mass number A and atomic number Z) emits 3α- particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will be :
Isotope of parent
Curie is a unit of
energy of gamma rays
half - life
radioactivity
intensity of gamma rays
In the nucleus of 11Na23, the number of protons, neutrons and electrons are
11, 12, 0
23, 12, 11
12, 11, 0
23, 11, 12
A sample of radioactive elements contains 4 x 1010 active nuclei. If half-life of element is 10 days, then the number of decayed nuclei after 30 days is.
0.5 × 1010
2 × 1010
3.5 × 1010
1 × 1010
A radioactive sample with a half-life of 1 month has the label: ‘Activity = 2 microcurie on 1 – 8 – 1991’. What would be its activity two months earlier?
1.0 microcurie
0.5 microcurie
4 microcurie
8 microcurie
