Nuclear Radiation and Radioactivity
Cathode-ray tubes consist of two metal plates sealed in a in a glass tube from which most of the air has been evacuated. When the metal plates are connected to a high-voltage source, the negatively charged plate, called the cathode, emits an invisible ray. The cathode ray is drawn to the positively charged plate, called the anode, where it passes through a hole and continues travelling to the other end of the tube. When the ray strikes the specially phosphor-coated surface, it produces bright light.
In 1895, Wilhelm Röntgen a German physicist discovered that cathode rays caused glass and metals to emit another type of ray. This highly energetic radiation could penetrate matter, darkened covered photographic plates, and cause some substances to fluoresce (give off light). Unlike cathode rays, these rays were not deflected by a magnet meaning that they did not contain charged particles. Röntgen called them X-rays due to its mysterious nature.
Shortly after, Antoine Becquerel a French physicist while studying the fluorescent properties of some substances, discovered that exposing wrapped photographic plates to a uranium compound caused them to darken. Like the X-rays, the rays from the uranium compound were highly energetic and could not be deflected by a magnet, however unlike X-rays they were emitted spontaneously.
Marie Curie one of Becquerel’s students at the time, suggested the name of radioactivity to describe the spontaneous emission of particle and/or radiation from elements.
There are three types of rays produced by the spontaneous breakdown, or decay, of substances such as uranium. Alpha (α) rays consisting of positively charged particles, Beta (β) rays which are electrons negatively charged particles and Gamma (γ) rays which are high energy radiation.
Three types of rays emitted by radioactive elements:
Beta (β) rays which consists of negatively charged particles (electrons).
Alpha (α) rays which are positively charged particles.
Gamma (γ) rays which are not particles but pure radiation.
The following video about Nuclear Radiation, covers the history of its discovery, explains the different types of radiation and the effect of radiation on living things and the environment:
The following video is named Radioactivity: How much can the Body Take?
It includes the following segments:
Radiation and the Atomic Bomb 06:06
Uranium Bomb Construction 00:43
Hiroshima: Eyewitness Account 02:51
Hiroshima Fatalities and Radioactive Damage 02:56
Hiroshima Survivors: Living Laboratories 05:31
Radiation and Cancer 01:20
Chernobyl: Radioactive Aftermath 06:50
Based on the information provided and what you have learned so far in this course, discuss the following:
What is the relevance of the discovery of radioactivity?