Alpha is the least penetrating, while gamma is the most penetrating. Radiation can be harmful, but it can also be useful.

The isotope of uranium capable of sustaining chain reaction is U-235.

One Joule is equal to 10⁷ ergs.

The power consumption of small devices is usually measured in Watts, and the power consumption of larger devices is measured in kilowatts (kW), or 1,000 Watts.

An instrument called ammeter measures electric current in a circuit. It is always connected in series in a circuit through which the current is to be measured. Also ammeter has negligible resistance, thus no voltage gets dropped across it.

Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks. In cosmic ray interactions, for example, such particles are ordinary protons and neutrons. Mesons are hadronic subatomic particles composed of one quark and one anti-quark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometre, which is about 2/3 the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through intermediate particles) to form electrons and neutrinos.

Thorium radioactive pollutant has recently drawn attention of public due to its occurrence in the building material.
Thorium is a naturally-occurring, slightly radioactive metal discovered in 1828 by the Swedish chemist Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. It is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium.
The alpha particles can travel only very short distances through most materials and cannot go through human skin.

Alpha ray is a positively charged particle emitted by a radioactive element.

Atoms are composed of Electrons and Nuclei.

Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.

Detergents used for cleaning clothes and utensils contains sulphonates. They are sodium salt of long chain benzene sulphonic acid or the sodium salt of a long chain alkyl hydrogensulphate.

The Uranium Lead Method, also known as the U-Pb method, is one of the most ancient and reliable radiometric dating methods. It is used to date rocks and crystals that were formed more than a billion years ago. It has a range of dating samples that are about 1billion to 4.5billion years old. It has a precision rate of 0.1−1 percent.

A chronometer measures time.

One kilometer is equal to 0.62 mile.

Kilohertz is a unit which measures electromagnetic radio wave frequencies.

Arsenous oxide is used for removing air bubbles from glass during its manufacture.

Electrical equivalent of one horsepower is 746 watts in the International System of Units (SI), and the heat equivalent is 2,545 BTU (British Thermal Units) per hour.