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
In a given reaction
ZXA → Z+1YA → Z-1KA-4 → Z-1KA-4
Radioactive radiations are emitted in the sequence of
α, β, γ
γ, α, β
β, α, γ
γ, β, α
Which of the following is used as a moderator in nuclear reactors?
Plutonium
Cadmium
Heavy water
Uranium
The most penetrating radiation out of the following is
γ-rays
α-particles
β-rays
χ-rays
The stable nucleus that has a radius half that of Fe56 is
Li7
Na21
S16
Ca40
A free neutrons decays into a proton, an electron and
a beta particle
an alpha particle
an antineutrino
an neutrino
Half-lives of two radioactive substances A and B are respectively 20 min and 40 min. Initially the samples of A and B have equal number of nuclei. After 80 min the ratio of remaining number of A and B nuclei is
1 : 16
4 : 1
1 : 4
1 : 1
The count rate of a Geiger Muller counter for the radiation of a radioactive material of half-life 30 min decreases to 5 s-1 after 2 h. The initial count rate was.
20 s-1
25 s-1
80 s-1
625 s-1
Curie is a unit of
energy of gamma rays
half-life
radioactivity
intensity of gamma rays
If the nuclear force between two protons, two neutrons and between proton and neutron is denoted by Fpp, Fnn and Fpn respectively, then
Fpp ≈ Fnn ≈ Fpn
Fpp ≠ Fnn and Fpp = Fnn
Fpp = Fnn = Fpn
Fpp ≠ Fnn ≠ Fpn