Why must a medical tracer be a gamma emitter?

Gamma radiation is the only type with enough penetration power to pass through the patient's body and reach the gamma camera or detector located outside the body.

What is the primary difference between irradiation and radioactive contamination?

Irradiation is the exposure of an object to radiation without the object becoming radioactive. Contamination occurs when radioactive particles actually get onto or into an object, making it a source of radiation itself.

Why is alpha radiation used in smoke detectors instead of gamma radiation?

Alpha radiation is highly ionizing, which is necessary to create a measurable current in the air gap. Gamma radiation is poorly ionizing and would not create enough ions to maintain a steady current for the sensor to monitor.

When monitoring the thickness of lead sheets, why might gamma radiation be used instead of beta?

Beta radiation is easily absorbed by thin metals like aluminum. For very dense or thick materials like lead, beta particles would be entirely blocked, whereas gamma rays have the penetration power to pass through and detect variations in thickness.

What is a common error when choosing a half-life for a medical tracer?

Choosing a half-life that is too long. If the half-life is days or years instead of hours, the patient remains radioactive for an extended period, significantly increasing the risk of long-term tissue damage and cancer.

Why is it a mistake to use an alpha emitter as a medical tracer injected into the body?

Alpha particles have very low penetration and would be completely absorbed by internal tissues before reaching an external detector. Furthermore, their high ionizing power would cause significant localized cell damage.

What error occurs if an industrial thickness gauge uses a source with a very short half-life?

The count rate at the detector would drop rapidly due to source decay rather than material thickness changes. This would lead to false readings and require constant, expensive recalibration of the machinery.

Define 'Radioactive Tracer' in a medical context.

A radioactive isotope, usually a gamma emitter with a short half-life, that is introduced into the body so that its path or accumulation can be mapped by an external detector to diagnose medical conditions.

What is 'Food Irradiation'?

The process of exposing food to high doses of gamma rays to kill bacteria, insects, and parasites. This extends shelf life and improves safety without making the food radioactive.

What does the term 'Ionizing Power' refer to?

The ability of radiation to knock electrons off atoms it collides with, creating charged ions. Alpha radiation has the highest ionizing power, while gamma has the lowest.

Uses of Radiation | Pearson Edexcel GCSE Physics

Ionizing radiation is utilized across medicine, industry, and domestic safety by exploiting the unique penetration powers, ionizing abilities, and decay rates of alpha, beta, and gamma emitters. The selection of a specific radioisotope depends on its ability to pass through materials and the duration of its activity, known as its half-life.

Uses of Radiation

Summary

1. Definition & Core Concepts