Question 151:
easyIn the given nuclear reaction, the element X is :
n$^{22}_{11}Na \rightarrow X + e^+ + \nu$
(2022)
This is a positron ($e^+$) emission process, where a proton converts into a neutron. The atomic number $Z$ decreases by 1, and the mass number $A$ remains unchanged. Final $Z = 11 - 1 = 10$, and $A = 22$. The resulting nucleus is $^{22}_{10}Ne$.
Question 152:
easyA radioactive nucleus $^{A}_{Z}X$ undergoes spontaneous decay in the sequencen$^{A}_{Z}X \rightarrow _{Z-1}B \rightarrow _{Z-3}C \rightarrow _{Z-2}D$, where Z is the atomic number of element X. The possible decay particles in the sequence are:
(2021)
Step 1: $Z \rightarrow Z-1$ indicates $\beta^+$ decay. Step 2: $Z-1 \rightarrow Z-3$ indicates a decrease of 2, which is $\alpha$ decay. Step 3: $Z-3 \rightarrow Z-2$ indicates an increase of 1, which is $\beta^-$ decay. The sequence is $\beta^+, \alpha, \beta^-$.
Question 153:
easyA certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u = 931 MeV):
(2013)
Total energy liberated is $E = \Delta m \times 931 = 0.02866 \times 931 = 26.68$ MeV $\approx 26.7$ MeV. The mass of the resulting Helium nucleus is approximately 4 u. The energy liberated per atomic mass unit is $26.7 / 4 = 6.675$ MeV.
Question 154:
easyEnergy is released in nuclear fission due to:
(2001)
In nuclear fission, a heavy nucleus splits into lighter, more stable nuclei. The binding energy per nucleon is higher for the fragments than for the parent nucleus. The increase in total binding energy is released as energy.
Question 155:
easyNuclear-Fission is best explained by:
(2000)
The liquid drop model of the nucleus, proposed by Bohr and Wheeler, best explains the phenomenon of nuclear fission. It compares the nucleus to a drop of incompressible liquid that can deform and split when it absorbs a neutron.
Question 156:
easyEnergy released in the fission of a single $^{235}U$ nucleus is 200 MeV. The fission rate of a $^{235}U$ filled reactor operating at a power level of 5 W is
(1993)
Power $P = 5 W = 5 J/s$. Energy per fission $E = 200 MeV = 200 \times 10^6 \times 1.6 \times 10^{-19} J = 3.2 \times 10^{-11} J$. The fission rate is $n = P/E = 5 / (3.2 \times 10^{-11}) = 1.56 \times 10^{11} s^{-1}$.
Question 157:
easySolar energy is due to
(1992)
The energy emitted by the sun and other stars originates from thermonuclear fusion reactions occurring in their extremely hot and dense cores, primarily the fusion of hydrogen into helium.
Question 158:
easyFusion reaction takes place at high temperature because:
(2011 Pre)
For fusion to occur, light nuclei must be brought very close together. A high temperature provides the nuclei with sufficient kinetic energy to overcome their mutual Coulombic repulsion.
Question 159:
easyIn any fission process the ratio (mass of fission products/mass of parent nucleus) is:
(2005)
In a fission process, energy is released. According to Einstein's mass-energy equivalence, this energy comes from a mass defect. Therefore, the total mass of the fission products is strictly less than the mass of the parent nucleus.
Question 160:
easyFission of nuclei is possible because the binding energy per nucleon in them:
(2005)
For heavy nuclei (high mass numbers), the binding energy per nucleon decreases as mass number increases. When a heavy nucleus undergoes fission into lighter, more stable nuclei, the binding energy per nucleon increases, releasing energy.