High School Teachers at CERN WWW.CERN.CH TEACHING MATERIALS VISITING CERN LINKS & BOOKS HST

## New ways of Doing Familiar Experiments

Simple Hertz Experiment

Half life game

Spectroscopy

Measuring the size of molecules

 1.)  Foam Chamber What we do need:      A box, with an open top (size: 20cm x 10 cm x 1cm) plexiglass                                    Stable foam from any detergent                                   Radioactive source  What we do:             Fill the box full of foam                                  Force the source above the box                                  Observe the surface of foam         What we can learn:       How long is the free way of alpha radiation                                             The slow particle is effective                                                              (idea: Kawakatsu Hiroshi, Japan)

 2. Simple Hertz Experiment       What we need:     A cardboard                                Two aluminum foil sheet 10cm x 6cm                                 Four pieces of copper wire ( about 7 cm) each                                A little Glimm bulb (from phase detector)                                 Stove igniter (piezoelectric)                                 Tape     What we do:      Radio signal sender                               Glue the two aluminum foil sheets to the carton                               Glue the two wire to the foils (see the figure)                                Connect them with the gas lighter                                Receiver:                                 Solder the two other wires to the end of bulb                                Push igniter, this will create sparks in the gap                                Close the receiver, and the bulb will lightening         You can make a diffraction grating from aluminum foil, and study the polarization of waves     What we can learn:  The principle of a Nobel prize experiment of Heinrich Hertz.                                                             (idea: Stray Cats, Japan)

 3.)     Home made GM counter       What we do need:     Two film tubes (plastic tube, that film comes in)                                       Wire, paper, gas (from gas lighter)                                       Aluminum Foil, screw                                      Pocket radio     What we do:             Make two holes in the first film tube (see the figure)                                       Put wires trough them                                      Put paper cylinder in the can                                      Fill with gas (from gas lighter), and close it                                      Make a capacitor (see the figure)                                       Connect the capacitor to a counter                                      Tune your pocket radio to static- no channels                                      You can listen the discharges due by particles on the radio      What we can learn:     The structure and principle of GM counter                                                                        (idea: Kawakatsu Hiroshi, Japan)

 4.) Game for to study of half life     What we need:        Coins or dice     What we do:          Have your class stand up                                   All the students have a coin                                   At the same time they should their coins all throw up                                   Those who threw a head, should sit down                                   Repeat it, and take down #`s.                                    You can change the ratio of probability with dice      What we can learn:     The random process is not chaos either.

 5.) Home made cloud chamber             What we need:          A heatproof glass bowl                                              A dark piece of cotton, or silk                                              Dry ice Alcohol Sponge                                              A piece of transistor cooler                                              Any charged object                                              Desk lamp                                              Tiny radioactive source (beta or alpha)              What we do:              Put dry ice in a plastic box                                              It must be broken, and a little alcohol poured onto it, and then put in the                                              transistor cooler                                              Pour a little alcohol (1-2 ml) onto a sponge around the bowl, put in the                                              source in the bowl.                                               Tightly wrap the top with plastic wrap                                              Put a bowl onto the transistor cooler                                              Wait a little bit, for the alcohol evaporate                                              Pass the charged object over the top of the wrap to clean the field of other                                              particles          What can we learn:       The principle of diffusion cloud chamber                                                                                                 (idea: Mori Yuji, Japan)

 Plastic wrap   Sponge glued around to sides of bowl Heatproof bowl Any dark synthetic textile Cotton   Heat insulator box (plastic foam)        Dry ice

 6.) Spark detector     What we need:          3000 V DC  (see the figure)                                      A metal plate                                     A wire (see the figure)                                      Radioactive source     What we do:           Join the detector to a voltage                                    Put a source above it.      What we can learn:     The principle of spark chambers                                                      (idea: Shiniichi Kishizawa)

 7.) Spectroscopy         What we need:         Stiff paper, plastic diffraction grating         What we do:            Cut out from the stiff paper the body of spectroscope (see the figure).                                          Make a round hole at the end of the tube (30 cm x 2,5 cm), and slit at the                                         other end.                                          You can glue the grating to the inside of the hole, and prepare the tube.                                          When you look through the hole, at the bottom of your viewing screen you will                                         see a spectrum.                                          If you have a bigger piece of grating, you can take a photo of a spectrum too.                                          Put the grating on a stable frame.                                          In a dark room you can find the spectrum, and take a photo. You must                                          experiment with the exposure time.                                                                                        (idea: Yanchai Yingprayoon, Thailand)

 8.) Collecting  radioactivity in the classroom  8/1      What we need:              A toy balloon                                          A Geiger-Muller counter                                          A  glass       What we do:               Blow up the balloon                                         Give it a charge (with silk, or with the hair of a longhaired girl)                                        Put it on the glass on the floor (insulator)                                         Wait 30 minutes until and let the balloon deflate                                         Hold the balloon up to the counter                                         Compare the count of impulses with the background  8/2        What we need:           Vacuum cleaner                                          Six layer of medical gauze, rubber ring                                          A Geiger-Muller counter        What we do:                We force the gauze to the end of the tube of vacuum cleaner.                                          Run the vacuum in the basement or in another poorly ventilated area                                          Take the gauze, and you can measure the radioactivity      What we can learn:      We live in continuous radiation.

 9.) Measurement of size of molecules        Introduction     The molecule: oleic acid, a long particle with one end hydrophilic, another -                              hydrophobic. It does not dissolve in water, but when a drop of oleic acid is put on                              the water surface it spreads out into                              Mono molecular layer (if it has enough place - one drop needs a surface of swimming                              pool!) To make an experiment possible in  school lab one has to dissolve  oleic acid in                              ethanol - which can be done without any restrictions.                              The best results are obtained in a 0.5% (volume) solution.      What we need:  oleic acid, ethanol, measuring cylinder, container to prepare solution, pipette                              (0.5 - 1 ml), cuvette, tap water, some fine powder, ruler .      What we do:          1. Prepare solution;                                    2. Fill the cuvette (like for developing pictures) with water and spread fine powder                                    light on its surface.                                    3. Using the pipette put one drop of solution on the surface;                                    4. Using the ruler measure the size of the oleic acid layer; remember, the ethanol                                    will dissolve in water.                                    5. Knowing how much the real volume of oleic acid was and what the size of layer                                    is you can calculate the size of the molecule.                                      Note: the size of the layer is about 20cm x20cm.