Conceptual Questions Based on Class 12 Physics Nuclei
Here we are providing conceptual questions based on Class 12 Physics Nuclei. Students are suggested to go through each and every question for better understanding.
Q.1. What is the ratio of the nuclear densities of two nuclei having mass numbers in the ratio 1:4?
Solution. As the nuclear density is independent of mass number, so the ratio of nuclear densities of the two given nuclei is 1: 1.
Q.2. What does exactly make heavy nuclei unstable?
Solution. Heavy nuclei are unstable due to the presence of large repulsive forces exerted between a large numbers of protons.
Q.3. Why is the number of neutrons in heavier nuclei more than the number of protons?
Solution. In a heavier nucleus, the force of repulsion between protons is appreciable due to the presence of a large number of protons. In order to exert large attractive nuclear force and hence to maintain stability of the nucleus, more neutrons become necessary for a heavier nucleus.
Q.4. Why is the density of a nucleus much more than that of the atoms?
Solution. The nuclear size is of the order of 10-14 m and atomic size is of the order of 10-10 m. So atomic size is 104 times the nuclear size while atomic mass is slightly greater than nuclear mass due to the presence of electrons. Hence nuclear density is much greater than atomic density.
Q.5. Why is the mass of a nucleus always less than the sum of the masses of its constituents, neutrons and protons?
Solution. When nucleons approach each other to form a nucleus, they strongly attract each other. Their potential energy decreases and becomes negative. It is this potential energy which holds the nucleons together in the nucleus. The decrease in potential energy results in the decrease in the mass of the nucleons inside the nucleus.
Q.6. Electrons cannot be a part of a nucleus, but protons can be a constituent part of it. Why?
Solution. This is because of the fact that the de-Broglie wavelength of electrons is larger than the size of the nucleus while that of protons is smaller than the size of the nucleus.
Q.7. What is the difference between a photon and a neutrino?
Solution. A photon is one quantum of electromagnetic radiation having zero rest mass, no charge, zero spin and no antiparticle. It has a fixed energy which depends on frequency. A neutrino is an elementary particle that accompanies a β-decay. It has zero rest mass, no charge and half spin. It has an antiparticle called antineutrino. It can have any energy from zero to any value permitted by the nuclear reaction. Its nature is non-electromagnetic.
