^Energy bands in solids Energy levels of electrons in an isolated atom are well defined & discrete, however the valence energy levels get modified drastically when atoms interact to form the lattice. If N atoms interact, then total 8 N energy valence energy levels are available which split in two bands (called VB & CB) […]
^Semiconductors Semiconductors (e.g. Si, Ge) belong to 14th group, thus have 4 valence electrons & hence from covalent bonds (temperature sensitive).
^Absorption radiations Radiations are absorbed by the materials according to the relation: I = I0 e-μ X Here μ = absorption coefficient I = intensity after penetrating the material through ‘x’ thickness of material I0 = intensity of the radiation before penetrating Absorption coefficient is highest for Pb.
^Commonly used abbreviations 1. R: Roentgen 2. Rad: Radiation absorbed dose 3. rem: Roentgen equivalent in man 4. RBE: Relative biological effectiveness
^Fission versus fusion
^Moderator The neutrons produced in fission of 235U nuclei have average KE about 2 MeV. Such neutrons are called fast neutrons. These fast neutrons have more tendency to escape instead of triggering another fission reaction. Slow neutrons are more efficient in inducing fission in 92U235 nuclei than fast neutrons. By the use of a moderator, […]
^Critical mass The minimum of Uranium needed to sustain chain reaction is called critical mass. It is 10 kg.
^Nuclear fuel Fissionable material is called nuclear fuel. The isotopes like U-235, Th -232 and Pu 239 can be used as the reactor fuel. A certain mass of the fuel is taken in the form of rods, tightly sealed in Aluminium containers. The rods, separated by moderator are placed in the core of the reactor.
^Uranium enrichment The 0.69% U235 is not sufficient to produce a self-sustaining critical chain reaction. To ensure high probability of chain reaction concentration of 235U has to be increased called enrichment. For reactors, the fuel must be enriched to 2.5-3.5%, U-235.
^Natural Uranium Found as uranium oxide (U2 O3) which when purified has a rich yellow color and is called “yellowcake”. Uranium has three isotopes namely: 92U238 (99.3%), 92U235 (0.69%) & 92U234 (0.01%). As the relative of abundance is highest for 92U238, it is called FERTILE. However fission is possible only with 92U235, thus is called […]
Our objective is to create a situation where students will find Physics interesting & the strongest subject helping them to achieve top ranks in competitive exams.
Copyright © 2021 KP Institute of Physics | Powered by RiAcub
Call 9872662552