Tuesday, June 29, 2010

New Institute of Physics Website

The UK-based Institute of Physics is a scientific charity devoted to increasing the practice, understanding and application of physics. It has a worldwide membership of over 36,000 and is a leading communicator of physics-related science to all audiences, from specialists through to government and the general public.

From the IoP blog:

After a year in development and following several usability studies, the Institute of Physics (IOP) is today re-launching its website http://www.iop.org/.With its increased user-friendliness, the website makes it easier to navigate around and quicker to find information. Content has been specifically tailored for teachers, students, media, IOP members and those with a general interest in the Institute and physics.
 There are separate links for teachers, students, and the general public.

I also found a link to the website Practical Physics -- with over 700 experiments!  Below is an explanation of how ion trails are formed from their page on cloud chambers:

Alpha particle tracks (from Practical Physics)

Nuclear 'bullets' from radioactive atoms make the tracks in a cloud chamber. They hurtle through the air, 'wet' with alcohol vapour, detaching an electron from atom after atom, leaving a trail of ions in their path. Tiny drops of alcohol can easily form on these ions to mark the trail.

The trail of ions is made up of some ‘air molecules’ that have lost an electron (leaving them with a positive charge) and some that have picked up the freed electrons, giving them a negative charge.

Alpha particle tracks

There is no sighting of the particle which caused the ionisation, because it has left the ‘scene’ before the condensation happens. If you count the number of droplets an alpha particle might produce 100,000 pairs of ions by pulling an electron from 100,000 atoms.

Alpha particle tracks
Nuclear 'bullets' forming a trail of ions which are condensation nuclei

When the alpha particle has lost all its energy in collisions with the ‘air molecules’ it stops moving and is absorbed.

2 comments:

  1. I really appreciate your enthusiasm in maintaining this blog with so many useful links.

    ReplyDelete
  2. Thanks! Even though we're now done with our year of physics, I will continue to add to it from time to time.

    ReplyDelete