The roentgen (R, also röntgen) is a unit of measurement for exposure

[RADboy]

The roentgen (R, also röntgen) is a unit of measurement for exposure to ionizing radiation (such as X-ray and gamma rays), and is named after the German physicist Wilhelm Röntgen. Adopted in 1928[1], 1 R is the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (esu or StatCoulomb) in one cubic centimeter of dry air at standard temperature and pressure (STP).


"1 R is the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge"
what exactly does this mean?

 

[Bob S]

Ionizing radiation liberates electrons from neutral atoms. 1 Roentgen of radiation liberates 1 statCoulomb of charge per cm³ of dry air.

Recall

22.41 liters of air contains about 29 grams of air (1 Avagadro's number of molecules) at STP.

1 statCoulomb is 3.33 x 10^-10 Coulombs.

About 34 eV (electron volts) of energy loss in air liberates 1 electron (1.6 x 10^-19 Coulombs).

1 rad (ionizing radiation energy dose) in air is defined as 100 ergs per gram.

So roughly 1 Roentgen ≈ 0.9 rads.

Please check my math.

Bob S