radsafety

Inverse Square Law

The intensity of radiation decreases with the square of the distance from the source. Formula: ( I_1 / I_2 = (D_2 / D_1)^2 ).

Half Value Layer (HVL)

The thickness of material required to reduce radiation intensity by half. Indicates the energy and penetrating power of the radiation beam.

Exposure (Gy)

A measure of the total energy of ions produced in air by radiation. Unit: Gray (Gy).

Absorbed Dose (Gy)

The amount of radiation energy absorbed by a material (e.g., tissue). Unit: Gray (Gy).

Effective Dose

A measure of the long-term biological effects of radiation exposure. Used for: Radiation workers and populations.

Radioactivity

The spontaneous release of energy from an unstable atom to reach a more stable state.

Cardinal Principles of Radiation Protection

Time: More time = more exposure. Distance: More distance = less exposure. Shielding: More shielding = less exposure.

Shielding

Materials used to reduce radiation exposure. Examples: Lead, concrete, protective apparel.

Time and Radiation Exposure

Directly proportional; more time = more exposure.

HVL and Beam Energy

Low HVL: Indicates low-energy, less penetrating radiation. High HVL: Indicates high-energy, more penetrating radiation.

Inverse Square Law Problem

If the exposure is 90mR at 1 foot, what is the exposure at 3.5 feet? Answer: 7.3mR.

HVL Problem

A single HVL for a beam is 40mm of copper. How much copper is needed to reduce the beam to less than 5% of its original intensity? Answer: 160mm (4 HVLs).

Time Problem

The exposure from a radiation source is 50Gy in 1 hour. What is the exposure in 30 minutes? Answer: 25Gy.

Inverse Square Law Formula

( I_1 / I_2 = (D_2 / D_1)^2 ).

HVL Calculation

Each HVL reduces intensity by half (e.g., 1 HVL = 50%, 2 HVLs = 25%, etc.).

Time and Exposure Relationship

Exposure is directly proportional to time (e.g., 1 hour = 50Gy, 30 minutes = 25Gy).