Illumination, UV & Ionic Radiation and Toxic Gases Measurement

Illumination is measured either in order to know the illumination itself, i.e. to obtain a value of this quantity expressed in lux or footcandles, or as an intermediate stage in ascertaining values of other photometric quantities, in which case it is usually sufficient to know the illumination as a relative value only. In the foregoing sections on the measurement of luminous flux and luminous intensity, examples of this procedure have already been given.

In principle there is no difference between the one kind of measurement of illumination and the other, but the distinction has to be made seeing that special instruments have been designed for use where the objective is the measurement of the illumination, these being adapted to the necessity of measuring this quantity in lighting installations. Portable illumination photometers, from which a direct reading of the illumination in lux or footcandles can be taken, need not, in general, be highly accurate, but reliable and compact in size; the cost should also be reasonable, so that this need not form an obstacle to the wide use of these very handy meters among lighting contractors, architects and so on.

UV & Ionic Radiation Measurement.

Ionizing radiation is radiation that has enough energy to remove electrons from atoms or molecules (groups of atoms) when it passes through or collides with some material. The loss of an electron with its negative charge causes the atom (or molecule) to become positively charged. The loss (or gain) of an electron is called ionization and a charged atom (or molecule) is called an ion.

There are natural and artificial sources of ionizing radiation. Artificial sources of radiation include X-ray machines, radioactive isotopes used in nuclear medicine, gamma cameras, nuclear gauges and nuclear power plants. X-rays refer to a kind of electromagnetic radiation generated when a strong electron beam bombards metal inside a glass tube. The frequency of this radiation is very high – 0.3 to 30 Ehz (exahertz or billion gigahertz). By comparison FM radio stations transmit at frequencies around 100 MHz (megahertz) or 0.1 Ghz (gigahertz).

Natural sources of radiation include:

• background radiation from space,
• cosmic radiation from cosmic rays,
• terrestrial radiation from minerals in the earth’s crust,
• radiation from inhaling radon gas,
• radiation from ingesting food and drinking water that may contain radioactive  potassium-40.

Minerals such as uranium and thorium are radioactive and give off radiation when the nucleus breaks down or disintegrates. The three kinds of radiation generated by radioactive materials or sources are alpha particles, beta particles and gamma-rays.