Dhristi JEE 2022-24

Introduction to Neutrino

The neutrino can be defined as an elementary subatomic particle with no charge and 1/2 unit spin. These fermions then react because of weak interaction and gravity. The rest mass of a Neutrino is almost negligible hence considered to be zero. The rest mass of a neutrino is comparatively very small than the elementary particles. Wolfgang Pauli discovered Neutrino in 1930, and the name was popularized in Science by the Italian Physicist Enrico Fermi. In Italians, The Neutrinos means “the little neutral ones” are electrically neutral particles, and their size is smaller than that of Neutrons. 


Properties and Types of Neutrino

Some of the most prominent properties of Neutrino are:

  • These Neutrinos belong to the family of leptons, this particle family has weak interactive forces. 

  • The Neutrino is of three basic kinds depending upon the charged lepton that they are associated with. These charged leptons are the electron, the muon, and the tau respectively. These associated electrons are named electron-neutrino, muon-neutrino, and tau-neutrino. 

  • A neutrino also has an antimatter component that is known as an antineutrino. The Neutrino and antineutrino together comprise a hot area of research in modern physics with many scientists and experts working in this field.

  • Neutrinos are not affected by the electromagnetic forces and hence, do not cause the ionization of matter. 

  • These Neutrinos react with matter only through extremely weak interactive forces.

  • They are also capable of passing through an enormous number of atoms without causing any reaction and hence these are the most penetrating subatomic particles.

  • The Neutrinos can also change a nucleus into another and this process is used in a radiochemical neutrino detector.


Neutrinos are found in various types in space. These types are:

As mentioned earlier, neutrinos are of three types or flavours and each of them has its respective properties. The first discovered neutrino is the electron-neutrino. Electron-neutrino has no electric charge and mass. It was discovered by Wolfgang Pauli to satisfy the energy loss in the process of radioactive beta decay. This particle is emitted along with a positron in positive beta decay. For negative beta decay, an electron with its antimatter particle that is an antineutrino is emitted.


Post the discovery of the second charge lepton, the muon, eventual identification of the second type of neutrino, the muon-neutrino started. Based on the results of a particle-accelerator experiment, high energy muon-neutrinos were discovered in 1962. They were produced from the decay of pi-meson. Though usually unreactive like other neutrinos, sometimes muon-neutrino reacts with protons and neutrons to produce muons.


In 2000, physicists experimentally showed the first evidence of the existence of the tau-neutrino. It was after the discovery of the tau leptons.


There are many active research areas involving neutrinos. Neutrino properties, testing predictions of their behaviour, and masses and rates of CP violation which is still unpredicted from the current theories. These subatomic particles are indispensable for the validation of the law of conservation of energy. They are related to radioactivity and play a very important role in nuclear physics. Knowledge of neutrinos and their properties enable physicists to understand the dynamics of several nuclear reactions. 

FAQs on Neutrino

1. What is the evidence for extra-terrestrial sources of Neutrinos?

The Extra-terrestrial sources of neutrinos are still a subject of infancy for many people. The only extraterrestrial object that was reported till the year 2018 was the Sun and the Supernova 1987A in the Large Magellanic Cloud. The branch of astronomy which deals with astronomical objects that are observed with the help of neutrino detectors in a special observatory is known as Neutrino astronomy. The radioactive decay and nuclear reactions take place inside the sun which is similar to the ones taking place in nuclear reactors or when atoms are hit by cosmic rays.  

2. What is a Neutrino Detector?

A neutrino detector is an apparatus used in physics to study neutrinos and their interactions. Since they are particles that only weakly interact with other matter particles, neutrino detectors are built to study these weak interactions. They are usually built underground so that the detector is isolated from cosmic rays and other background radiations. Various detection methods have been used for detecting neutrinos. Heavy water finds its use as a detection medium; some detectives also consist of large volumes of chlorine on gallium. These are periodically checked for excess argon and germanium which are created when neutrinos interact with the original substances. 

3. Give a brief description of the Neutrino?

To give a brief description, the Neutrinos can be considered subatomic particles which have no electric charge and negligible mass which is taken to be zero. The neutrino is a neutral particle that is smaller than the neutrons. The Neutrinos are from the family of leptons which are known to have very weak interactions. The rest mass of the neutrinos is taken as zero and it has ½ units spin. In nature, this process occurs in nuclear fusion taking place in the sun. It also occurs inside the nuclear reactors during nuclear fission and when cosmic rays strike atomic particles. 

4. What was the contradiction in the law of conservation of energy dealt with by Neil Bohr?

The Alpha and beta rays were discovered in 1899 by a physicist named Rutherford. The study of radioactive disintegrations led to the conclusion that alpha rays were ‘monokinetic’ and consumed the entire energy available in the decay while the Beta rays and on the other hand these Beta rays also took a certain part from the energy of the entire decay. This created a contradiction in the conservation of energy law. And this missing energy paradigm led Neil Bohr to propose that the conservation of energy law was not prevalent in all cases. This was considered a mortal sin for physicists in those days.

5. Give a brief account of the hypothesis of the Neutrino.

After the contradiction in the law of conservation of energy was established, a physicist named Wolfgang Pauli postulated the existence of an electrically neutral particle that is emitted along with a beta particle in the process of Beta decay which was a hypothetical third body that took the extra energy remaining after the Beta decay. Thus, the law of conservation of energy was saved. This hypothesis found support from an Italian Physicist named Enrico Fermi. The conference of Solvay in the year 1933 proposed that an electron-neutrino pair is spontaneously produced by the nucleus during beta decay. 

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