Enter the exposure rate constant (R-cm^2/hr*Ci), the source activity (Ci), and the distance (cm) into the Exposure Rate Calculator. The calculator will evaluate the Exposure Rate.

## Exposure Rate Formula

The following formula is used to calculate the Exposure Rate.

EX = R * a / r^2

• Where EX is the Exposure Rate (roentgen per hour)
• R is the exposure rate constant (R-cm^2/hr*Ci)
• a is the source activity (Ci)
• r is the distance (cm)

## How to Calculate Exposure Rate?

The following two example problems outline the steps and information needed to calculate the Exposure Rate.

Example Problem #1

1. First, determine the exposure rate constant (R-cm^2/hr*Ci).
• The exposure rate constant (R-cm^2/hr*Ci) is calculated to be : 12.838.
2. Next, determine the source activity (Ci).
• The source activity (Ci) is measured to be: 5.
3. Next, determine the distance (cm).
• The distance (cm) is found to be: 2.
4. Finally, calculate the Exposure Rate using the formula above:

EX = R * a / r^2

The values provided above are inserted into the equation below and computed.

EX = 12.838 * 5 / 2^2 = 16.0475 (roentgen per hour)

Example Problem #2

The variables required for this problem are provided below:

exposure rate constant (R-cm^2/hr*Ci) = 6

source activity (Ci) = 7

distance (cm) = 8