Science & Technology in Action

9th Edition

Xrays: Uses and Dangers

Radiological Protection Institute of Ireland

The use of X-rays in any situation carries some risk and accordingly such use is carefully monitored by the RPII. This lesson describes the nature of X-rays and their position in the electromagnetic spectrum. The production of X-rays for medical application is discussed.

Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Although X-rays have many uses people generally associate them with their use in medical diagnostics. X-rays can pass through soft body tissues relatively easily but are stopped to some extent by denser tissues such as bone. For many years after their discovery in the 1870s, scientists investigated their properties but were largely unaware of the dangers associated with them.

As with all sources of ionising radiation, their use results in a radiation dose and an increased risk of cancer later in life. Small doses from diagnostic X-rays carry a small risk, large doses or repeated use carries a higher risk.

The German physicist Wilhelm Röntgen is usually credited with the discovery of X-rays in 1895, but others were aware of their existence about twenty years earlier but had not studied them to the same extent. Röntgen took an X-ray photograph of his wife’s hand to demonstrate their possible medical use.

What are X-rays?
X-rays are electromagnetic waves having the same nature as visible light, ultra violet, infrared, radio waves and microwaves, etc. These types of electromagnetic radiation differ in their wavelength; those with shorter wavelength have greater energy. The energy of photons of ultraviolet and X-rays is sufficient to break chemical bonds and so these radiations are said to be ionising. Gamma rays are like high energy X-rays and are mainly produced in nuclear interactions such as radioactive decay. Cosmic rays, which are believed to come from exploding stars (supernovae), have even greater energy than gamma rays; they have been found to consist mainly of high energy protons and are largely blocked by the atmosphere. They generate gamma rays when they collide with molecules in the atmosphere or indeed in living things.

To read the full lesson, download the pdf above.

Quiz questions

  1. X-rays are non-ionising. false
  2. The typical energy of medical X-rays is hundreds of times greater than that of visible light. true
  3. The typical energy of microwaves is hundreds of times less than that of visible light. true
  4. X-rays were discovered by Marie Curie. false
  5. The X-rays used in examining welds in metal are more penetrating than medical X-rays. true
  6. The maximum energy of X-rays is directly proportional to the voltage used to generate them. true
  7. There is no danger associated with medical X-rays. false
  8. Most of the ionising radiation we receive is artificial. false
  9. Mobile phones emit ionising radiation. false
  10. The average dose of ionising radiation that people in Ireland receive is about 4000 microsievert per annum. true
  11. Hard X-rays have shorter wavelength than soft X-rays. true

Glossary of terms

chemical bond
cosmic rays
directly proportional