Radiation and Radioactive Decay

What it shows:

In a nuclear reactor or atom bomb, a fissile material such as 235U can capture a neutron. The resulting unstable nucleus fragments into two smaller nuclei, releasing energy and several neutrons (a typical equation is given below). Each of...

What it shows:

This block of uranium is of great historical significance -- it is a remnant of the WWII German Atomic Bomb Project. It was brought to Harvard by Prof. Edwin C. Kemble, Physics Dept. Chairman and also Deputy Science Director of the ALSOS...

We have designed and built our own cosmic ray telescope (a.k.a. spark chamber). Unlike the old one, this one works reliably, is larger, and makes for a great demo.

In the 1960's and '70s, spark chambers were commonly used as detectors in particle physics...

What It Shows

The path of a single charged particle can be made visible in cooled supersaturated air/alcohol vapor.

How It Works

The cloud chamber was developed by C.T.R. Wilson at the turn of the century (he received the Nobel Prize in 1927 for his...

What it shows:

One of the more important discoveries in modern physics is the production of isotopes (both radioactive and stable) by the capture of neutrons. ¹ In this experiment the bombardment of silver by thermalized neutrons produces short lived...

What it shows:

The very first determination of a half-life for a radioactive decay was made by Rutherford. ¹ In a study of the properties of thorium emanation, he found that the intensity of the radiations fell off with time in a geometric progression...

What it shows:

Gamma ray spectroscopy is used to detect the minute amount of radioactive potassium-40 present in the human body. Using a NaI(Tl) scintillation detector in conjunction with a multichannel pulse-height analyzer (PHA), 1.46 MeV gammas...

Observe the decay of airborne radionuclides with a Geiger counter and computer. (OK, it's not new since we've been doing the experiment for 20 years...we just neglected adding it to our list.)

What it shows:

Filtering dust particles from the air is a...

What it shows:

β-rays emanating from a radioactive isotope are deflected from their straight line paths by a magnetic field.

How it works:

⁹⁰Sr/⁹⁰Y, a "pure" beta-minus source, emits a continuous spectrum of fast electrons up to a maximum energy of 0.546/2...

What it shows:

Gamma rays are electromagnetic radiations which we detect as quanta of energy or photons. When the radioactive source is confined so that it acts as a point source, the diminution in the number of photons incident on a given area is such...