Scintillation counter (scintillometer) : An instrument which measures gamma radiation. It is also used in airborne and ground radiometre surveys. This instrument utilizes the flash of light emitted when the atoms of a suitable ‘phosphor’ are energized by gamma rays. The scintillations are detected by a light-sensitive cathode.

Yellow cakes generally denotes various compounds of uranium like uranium oxides.

Nuclear fission is a perfect example of chain reaction. In case of nuclear fission a heavy atomic nucleus (such as that of uranium) disintegrates into two nearby equal fragments with release of large amount of energy when large number of nuclei are brought closer together. In such a case the neutrons released, when one nucleus splits, strikes other nuclei causing them to split and the process continues. Now atomic bomb and nuclear reactor both works on nuclear fission chain reaction but chain reaction in nuclear reactor is controlled by control rods, made up of metal cadmium or boron a neutron absorbing material, whereas in atomic bomb there is no neutron absorber. So chain reaction goes uncontrolled and is very violent.

Each alpha particle contains two protons and two neutrons.
Total number of nucleons = Number of protons + Number of neutrons = 2 + 2 = 4
Total number of nucleons = Mass number of an element
Thus mass number of alpha particle is 4 which is equal to molecular weight of helium atom.

Raja Ramanna India’s Most Eminent Nuclear Physicist, if we have today achieved the status of a “developed country” in nuclear science and technology, it is in large measure a consequence of Dr. Ramanna’s ideals, policies and efforts.
M. S. Swaminathan is an Indian agriculture scientist. He is known as the “Father of the Green Revolution in India.”
Udipi Ramachandra Rao is a space scientist and former chairman of the Indian Space Research Organisation. Prof Rao’s experiments on a number of Pioneer and Explorer spacecrafts, led to a complete understanding of the solar cosmic ray phenomena and the electromagnetic state of the interplanetary space.
Meghnad Saha was an Indian astrophysicist, best known for his development of the Saha equation, used to describe chemical and physical conditions in stars.

Zirconium purified metal is primarily used by the nuclear industry to form the outer layer of fuel rods in nuclear reactors. Zirconium’s major use is as cladding for nuclear reactors. It is ideal for this use, as it has a limited ability to capture neutrons, strength at elevated temperatures, considerable corrosion resistance, and satisfactory neutron damage resistance.

Barium is given in adequate amount to patients before X-ray examination. The gut (gastrointestinal tract) does not show up very well on ordinary X-ray pictures. However, if you drink a white liquid that contains a chemical called barium sulphate, the outline of the upper parts of the gut (oesophagus, stomach and small intestines) shows up clearly on X-ray pictures. This is because X-rays do not pass through barium.

Cobalt-60 is useful as a gamma rays source because it can be produced in predictable quantity and high activity by bombarding cobalt with neutrons. This is commonly used in radiation therapy for treatment of cancer.

Ammonia is used as a large scale refrigerant because it has highest refrigerating capacity per pound of any refrigerant and a number of other excellent thermal properties that make it popular for a number of refrigeration applications in spite of its being toxic, explosive and flammable within certain conditions. Ammonia is used as refrigerant prominently in the refrigeration systems of food industry like dairies, ice creams plants, frozen food production plants, cold storage warehouses, processors of fish, meat and number of other applications. Comparatively chlorofluorocarbon (CFC) chemical, safer refrigerators were possible for home and consumer use.

Mixing of methane with air is the cause of most mining explosions.

Aufbau principle states that ‘in the ground state of the atom, the orbitals are filled in order of their increasing energies, starting with the orbital of lowest energy’. The word aufbau is German word which means building up.
The increasing order of energy and hence that of filling of orbitals is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p.

As it is given that half life of given substance is 4 months.
The amount of substance left after 4 months = 1/2
The amount of substance left after 8 months = 1/4
Therefore the amount of substance decay in 8 months = [1 – (1/4)] = 3/4

Zirconium is non-radioactive substance as the substance which have atomic number above 80 shows radioactivity. The rest three Astatine, Francium and Tritium are radioactive in nature. There are five naturally occurring isotopes of Zirconium: Zirconium-90, Zirconium-91, Zirconium-92, Zirconium-94 and Zirconium-96. Natural Zirconium has two radioactive isotopes 94Zr & 96Zr. Three stable isotopes of Zirconium also found in nature, which account for 79.82% of the total amount.

The Standard Model of particle physics assumed that neutrino are massless.
A quark is an elementary particle and a fundamental constituent of matter. Quarks have fractional electric charge values either –1/3 or +2/3 times the elementary charge.
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and the same mass as an electron.
In physics, a photon is an elementary particle. Spin of a photon can be –1 or +1. In a classical view we can say that one is spinning right and other to the left.

Ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Following the aphorism, “like dissolves like”, ionic compounds dissolve in polar solvents, especially those that ionize, such as water and ionic liquids. They are usually appreciably soluble in other polar solvents such as alcohols, acetone. Solid ionic compounds cannot conduct electricity because there are no mobile ions or electrons present in the lattice.

Magnetic quantum number represents the number of orbitals present in the sub-shell magnetic quantum number about the orientation of the orbital.

Liquid sodium is used as a coolant because water is difficult to use as a coolant for a fast reactor because water acts as a neutron moderator that slows the fast neutrons into thermal neutrons. While it may be possible to use supercritical water as a coolant in a fast reactor, this would require a very high pressure. In contrast, sodium atoms are much heavier than both the oxygen and hydrogen atoms found in water, and therefore the neutrons lose less energy in collisions with sodium atoms. Sodium also need not be pressurized since its boiling point is higher than the reactor’s operating temperature. A disadvantage of sodium is its chemical reactivity, which requires special precautions to prevent and suppress fires. If sodium comes into contact with water it explodes, and it burns when in contact with air.

Crookes glass is a type of glass that contains cerium and other rare earths and has a high absorption of ultraviolet radiation used in sunglasses.

A dry cell has the electrolyte immobilized as a paste, with only enough moisture in the paste to allow current to flow. The electrolyte is ammonium chloride in the form of a paste next to the zinc anode. In some more modern types of so called ‘high power’ batteries, the ammonium chloride has been replaced by zinc chloride.

A hydrogen vehicle is an alternative fuel vehicle that uses hydrogen as its onboard fuel for motive power. The hydrogen vehicle use hydrogen fuel cell for generation of motive power. These fuel cell in which hydrogen serve as a fuel and oxygen as an oxidant emits exhaust of water.