Brief description:
Cloud chambers are boxes specially made to
detect charged particles and radiation. In this
activity, a cloud chamber is used to observe
alpha and beta particles, the charged products
of the radioactive decay of thorium-232.
Students should already have been introduced
to the concept of radioactive decay and the
differences between alpha and beta radiation.
This experiment will assist students in
their understanding by providing a physical
demonstration of radioactive decay.
Students will observe the condensation trails
that charged particles leave in their wake in a
cloud chamber, and learn to identify particles
based on the trail properties. Trails made by cosmic rays can be seen in the cloud chamber, which could provide a starting point for introducing cosmic rays and their deflection
by the Earth’s magnetic field. Students will practice calculating and writing radioactive
decay equations. Implications of radiation
for ESA are discussed, including the negative
effects of radiation on circuits, and the use of
radioactive decay as a power source.
Subject:
Science, Chemistry, Physics
Learning Objectives:
Learn about fundamental particles and how they interact, including the interactions between charged particles and
magnetic fields
Define atomic number and mass number
Discover radiation and radioactive decay, and how it can be used as a power source for
spacecraft
Investigate the negative effects of ionising radiation on
electronics
learn about cosmic rays including their interactions with
the atmosphere
Improve general experimental skills including using
equipment appropriately and making and
recording observations.
Communicate and discuss results, ask relevant questions to
expand understanding and knowledge of a
subject.
Apply knowledge gained
through experimental observations to solve
theoretical problems.
Age range:
14 – 18 years old
Time
Preparation: 5 minutes per cloud chamber
Lesson: 1 hour
Resource available in: English, French, and Italian.
Activity 1: Building a cloud chamber
In this hands-on experiment, students will build their very own cloud chamber, allowing them to observe the radioactive decay of thorium-232, a radioactive thorium isotope.
Alpha and
beta emission can be observed in the form of condensation trails (contrails) in the alcohol vapour
inside the chamber, allowing us to better unders
Equipment To prepare in advance:
Medium-sized plastic fish tank
Adhesive-backed felt (or normal felt and glue appropriate for felt and plastic)
To perform the experiment:
Two thoriated tungsten welding rods (or other alpha/beta source)
About 2.5 kg dry ice (solid CO2)
20 ml isopropyl alcohol, also known as isopropanol (or ethanol if this is unavailable)
A plastic fish tank with pre-attached felt
Two metal trays (baking trays work well)
One piece of black card or laminated black paper (to line trays if they are not dark)
One or two intense light sources (e.g. an LED light strip, torch, or slide projector light)
A sheet of paper to wrap around one rod
Poster putty or reusable adhesive
A pipette
Thermal protective gloves
Safety glasses (one pair per person)
Activity 2: Test your knowledge of
radioactive decay
In this activity, students will discuss the topics explored in the experimental stage, and complete activities to test their knowledge.
Equipment
Student worksheet printed for each student
Pen/pencil
Did you know?
On Earth we are protected from charged cosmic rays by a magnetic field, the magnetosphere, which is generated by
the motion of magnetic elements in the Earth’s core. The magnetic field extends almost twice the distance of the
Moon but the further from the Earth, the weaker it is and so there is less protection from ionising space particles.
The NASA/ESA/ASI Cassini Huygens mission to Saturn
had to cope with this cosmic
radiation as it ventured far beyond the edge of the magnetosphere.
Once Cassini-Huygens reached its destination, it was protected by
Saturn’s own powerful magnetic field.
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