Question

a. How does a Geiger counter detect radiation? b. What are the SI and common units that describe the activity of a radioactive sample? c. What are the SI and common units that describe the radiation dose absorbed by tissue? d. What is meant by the term kilogray?

Short answer

A Geiger counter detects radiation by ionizing gas in a Geiger-Müller tube. The SI unit for radioactivity is the becquerel, and the gray is for absorbed dose, with kilogray being 1,000 grays.

Step-by-step solution

Understanding Geiger Counters

A Geiger counter detects radiation by using a Geiger-Müller tube filled with a low-pressure gas. When radiation enters this tube, it ionizes the gas, causing an electrical discharge that can be measured and counted. This indicate the presence of radioactive particles.

Units for Radioactive Activity

The SI unit for describing the activity of a radioactive sample is the becquerel (Bq), which is defined as one disintegration per second. A common unit used is the curie (Ci), where 1 Ci = 3.7 × 10^10 disintegrations per second.

Units for Radiation Dose Absorbed

The SI unit to describe the absorbed dose of radiation in tissue is the gray (Gy), which is defined as 1 joule of radiation energy absorbed per kilogram of tissue. A common unit used is the rad, where 1 rad = 0.01 Gy.

Meaning of Kilogray

A kilogray (kGy) is a non-SI unit used to measure absorbed radiation dose, where 1 kilogray equals 1,000 grays.

Key concepts

Geiger counter

A Geiger counter is a device designed to detect and measure radiation. At its core, it contains a Geiger-Müller tube, which is filled with a low-pressure gas. When radiation enters this tube, it ionizes the gas inside. The ionization process produces charged particles. These particles create an electrical current by moving towards electrodes within the tube. This current generates a signal that is counted and often converted into an audible click or visual display.
Geiger counters are highly sensitive to different types of radiation, such as alpha particles, beta particles, and gamma rays. The amount of radiation detected is typically shown as counts per minute (cpm) or counts per second (cps), reflecting how much radiation is interacting with the device.

radioactive activity units

Radioactive activity measures how many atoms in a sample decay per unit time. This decay is quantified in units of activity. The SI unit for radioactive activity is the becquerel (Bq). One becquerel equals one disintegration per second.
Another common unit is the curie (Ci). One curie is equal to 3.7 × 10^10 disintegrations per second. Thus, 1 Ci = 3.7 × 10^10 Bq. Curie is named after Marie Curie, the famed physicist who conducted pioneering research on radioactivity.
Understanding these units helps in determining the level of radioactivity in a given sample, which is essential for applications in medical treatments, nuclear energy, and radiation safety.

absorbed radiation dose units

Absorbed radiation dose quantifies the amount of radiation energy that is absorbed by tissue. The SI unit for absorbed dose is the gray (Gy). One gray is defined as one joule of radiation energy absorbed per kilogram of tissue.
A commonly used non-SI unit is the rad (radiation absorbed dose). One rad is equal to 0.01 gray. In practical terms, 1 Gy = 100 rad. The concept of absorbed dose is critical in environments such as healthcare (for radiology and cancer treatment), radiation protection, and nuclear reactor operations.
By measuring the absorbed dose, we can assess the potential biological effects of radiation exposure on human tissue, helping to ensure safety and effective dose management.

kilogray

A kilogray (kGy) is a unit that measures high doses of absorbed radiation. Specifically, one kilogray is equivalent to 1,000 grays. This unit is used in contexts where extremely high doses are relevant, such as in radiation processing industries, including food irradiation and sterilizing medical equipment.
For example, if a material is exposed to a dose of 3 kGy, it means it has absorbed 3,000 grays of radiation. The kilogray is convenient for expressing large doses in a manageable number, simplifying calculations and communication.