# Units and Quantities

Unit (Symbol)DefinitionUnits
Exposure (X)
Amount of ionization per mass of air due to X-rays and gamma rays.Roentgen (R)
Absorbed Dose (D)
Amount of energy imparted by radiation per unit mass.SI: Gray (Gy)

1 rad = 0.01Gy
Kerma (K)
Kinetic Energy Released per unit MAss
Kinetic energy transferred by uncharged particles to charged particles per unit mass.
SI: Gray (Gy)

1 rad = 0.01Gy
Equivalent Dose (HT)
A measure of absorbed dose weighted for the biological effectiveness
of the types(s) of radiation (relative to the low LET photons and electrons)
to produce stochastic health effects in humans.
SI: Sievert (Sv)

1 rem = 0.01Sv
Dose Equivalent (H)
A measure of absorbed dose weighted for the biological effectiveness of
the types of radiation (relative to low LET photons and electrons) to
produce stochastic health effects in humans.
Sievert (Sv)

1 rem = 0.01Sv
Effective Dose (E)
A measure of equivalent dose, weighted for the biological sensitivity of
the exposed tissues and organs (relative to whole body exposure) to
stochastic health effects in humans.
Sievert (Sv)

1 rem = 0.01Sv
Effective Dose
Equivalent (HE)

A measure of equivalent dose, weighted for the biological sensitivity of
the exposed tissues and organs (relative to whole body exposure) to
stochastic health effects in humans.
Sievert (Sv)

1 rem = 0.01Sv

# Conversion Factors

### Energy

• $$Joule (J) = Electron Volt (eV) \times 1.602 \times 10^{-19}$$

• Air Collision Kerma (Gy)

### Temperature

• Degrees Kelvin (K) = Degrees Celsius (C) + 273.16

# Units

 Physical Quantity Unit Name Symbol Charge (electric) Coulomb C Dose Gray Gy (=J/kg) Energy Joule J Energy Electron Volt eV Exposure Roentgen R Length Meter m Mass kilogram kg Time second s Time minute min

# Metric Unit Prefix

 Prefix Symbol Base 10 Decimal yotta Y 1024 1,000,000,000,000,000,000,000,000 zetta Z 1021 1,000,000,000,000,000,000,000 exa E 1018 1,000,000,000,000,000,000 peta P 1015 1,000,000,000,000,000 tera T 1012 1,000,000,000,000 giga G 109 1,000,000,000 mega M 106 1,000,000 kilo k 103 1,000 hecto h 102 100 deca da 101 10 100 1 deci d 10-1 0.1 centi c 10-2 0.01 milli m 10-3 0.001 micro μ 10-6 0.000,001 nano n 10-9 0.000,000,001 pico p 10-12 0.000,000,000,001 femto f 10-15 0.000,000,000,000,001 atto a 10-18 0.000,000,000,000,000,001 zepto z 10-21 0.000,000,000,000,000,000,001 yocto y 10-24 0.000,000,000,000,000,000,000,001