Einstein gave a famous theory called theory of relativity in which he showed that the mass & energy are interrelated & interchangeable. Einstein's mass energy relation states that the energy E produced by a change of mass (∆m) is given by
where, c is the velocity of light in vacuum.
Einstein's mass energy relation explains that when there is loss of mass during any process then an equivalent amount of energy is produced.
The difference in mass between the actual mass of the nucleus and the masses of the constituent nucleons is called mass defect. Let us consider a nucleus of mass M, atomic number Z with mass of protons MZ and mass number A then the nucleus is made up of (A-Z) neutrons each of mass MN. The mass defect is given as:
Mass Defect = [ZMZ+ (A - Z)MN -M]
where, ∆x is uncertainty in the measurement of position & ∆p is uncertainty in the measurement of momentum. This expression is known as uncertainty relation. From relation 1, if uncertainty in position is reduced, the uncertainty in momentum is increased & vice-versa. It means that certainty of determination of one property introduces uncertainty for the determination of other.
Binding energy of the nucleus is the total work or energy required to take all the nucleons apart so that they are completely separated. mass-defect is the measure of binding energy. Binding energy is defined as the mass-defect multiplied by c2.
Binding energy of nucleus = mass-defect.c2 = [ZMZ+ (A - Z)MN -M].c2
When the emission of energy is made more than absorption, the amplification takes place. Energy is amplified & made coherence which produce LASER. This is the basic principle behind the working of LASER.
32. Does the gaseous discharge occur at very low pressure?
No, the gaseous discharge does not occur at very low pressure. At low pressure, the density of a gas is also very low inside the tube so there is very much less possibilities for the collision of electrons emitted from cathode with gas molecules & finally the probability of collision becomes zero. Hence, no discharge is observed at very low pressure.
92U235 + 0n1 = 57La148 + 35Br85 + 30n1 + Q
Point out the difference between nuclear fission and fusion.
The difference between nuclear fusion & fission are as follows:
|Nuclear fusion:||Nuclear fission;|
|1. Nuclear fusion is the process of fusion of two light nuclei to form a heavier nucleus with the liberation of energy.||1. Nuclear fission is the process of splitting of a heavy nucleus into two lighter nuclei with the liberation of energy.|
|2. It does not need bombardment of neutron.||2. It needs bombardment of neutron.|
|3. The energy produced is less than the energy produced during nuclear fission.||3. The energy produced is more than the energy produced during nuclear fusion.|
|4. This process occurs in the sun & stars.||4. This process does not occur in the sun or stars.|
Inside the nucleus, the protons repel each other due to electrostatic repulsion of like charges. So, for the nucleus to be stable there must exist other forces between the nucleons rather than gravitational force. These are called nuclear forces. Nuclear forces have short range, shorter than the interatomic distances and much stronger than electromagnetic interactions. They provides a net attractive force greater than the sum of gravitational and electrostatic force. So, the nucleus are stable.
92U235 + 0n1 = 57La148 + 35Br85 + 30n1 + QFission of 92U235 nucleus occurs when a neutron of air bombards an atom of Uranium. Each fission will produce three neutrons having kinetic energy. Three of them having sufficient energy will again bombard the three nucleus of Uranium nucleus resulting three more fission reactions. From three fission reaction more nine neutrons are produced. The process goes on until all Uranium atoms take part in the reaction with release of huge amount of energy.
During a chain nuclear fission reaction, if the fission neutrons may become sufficient to create controlled multiple fission reaction by removing some of the fission neutrons with production of large quantity of energy is called controlled chain reaction. Here, the nuclear reaction goes on slowly without any explosion or danger. The chain reaction may be made to proceed slowly and in a controlled manner & the device for accomplishing a controlled chain reaction is called nuclear reactor.
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