Hots Questions

## Nuclei

- Think before you solve
1
Radioactive decay law states that radioactive samples decay exponentially. But what can you say about the disintegration probability of a single nuclide. Is the disintegration probability the same for every nuclide?
Consider two nuclei of same radioactive nuclide. One of the nuclei was created in a supernova explosion billion years ago. The other was created in a nuclear reaction minutes ago. The probability of decay during next time is
A
different of each nuclei
B
nuclei created in explosion decays first
C
nuclei created in the reactor decays first
D
independent of time of creation
2
What determines the decay rate of a of a radioactive sample? Is it related to the energy released?
Assertion
In alpha decay of different radioactive nuclides, the energy of alpha particles has been compared. It is found that as the energy of alpha particle increases the half-life of the decay goes on decreasing.
Reason
More is the energy in any decay process, more is the probability of decaying the nuclide which leads to faster rate of decay.
A
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C
Assertion is correct but Reason is incorrect
D
Assertion is incorrect but Reason is correct
3
Does the process of spontaneous alpha decay obey the law of conservation of momentum?
A stationary thorium nucleus emits an alpha particle with kinetic energy . What is the kinetic energy of the recoiling nucleus?
A
B
C
D
4
What is the reason behind stable nuclei not having more protons than neutrons?
STATEMENT-1:
The plot of atomic number (y-axis) versus number of neutrons (x-axis) for stable nuclei shows a curvature towards x-axis from the line of  slope as the atomic number is increased.
STATEMENT-2:
Proton-proton electrostatic repulsions begin to overcome attractive forces involving protons and neutrons and neutrons in heavier nuclides.
A
STATEMENT-1 is True, STATEMENT-2 is True; STATEMENT-2 is correct explanation for STATEMENT-1
B
STATEMENT-1 is True, STATEMENT-2 is True; STATEMENT-2 is NOT a correct explanation for STATEMENT-1
C
STATEMENT-1 is True, STATEMENT-2 is False
D
STATEMENT-1 is False, STATEMENT-2 is True
5
How can we check the feasibility of a nuclear reaction using the binding energy per nucleon curve?
The above is a plot of binding energy per nucleon , against the nuclear mass correspond to different nuclei. Consider four reactions :
(i)
(ii)
(iii)
(iv)
where is the energy released ? In which reaction is positive ?
A
(i) and (iv)
B
(i) and (iii)
C
(ii) and (iv)
D
(ii) and (iii).
6
decay and electron capture are two competing processes. Can you show that one reaction is energetically possible and the other is not?
For the (positron) emission from a nucleus, there is another competing process known as electron capture (electron from an inner orbit, say, the K shell, is captured by the nucleus and a neutrino is emitted).

Show that if  emission is energetically allowed, electron capture is necessarily allowed but not vice versa.