Promoting physics supporting physicists Cloud Chamber Workshop Promoting

Promoting physics, supporting physicists Cloud Chamber Workshop

Promoting physics, supporting physicists

Cancer Promoting physics, supporting physicists

Promoting physics, supporting physicists

Promoting physics, supporting physicists Dry ice Solid carbon dioxide. Subliming at -78. 4ºC ALWAYS store dry ice in an area which is: Well ventilated (it's an asphyxiant). Preferably not below ground (because it's heavier than air). Out of direct sunlight and sources of heat (so it lasts longer) Secure – to prevent unauthorised access. DO NOT handle dry ice with bare hands. It can cause severe cold burns and frostbite. DO NOT PLACE IN WORKING REFRIGERATOR / FREEZER REMEMBER – A little bit of dry ice will sublime to a large volume of CO 2 gas. CLEAPSS General Handbook Section 11. 2

Promoting physics, supporting physicists Cloud Chambers The Nobel Prize in Physics 1927 was divided equally between Arthur Holly Compton "for his discovery of the effect named after him" and Charles Thomson Rees Wilson "for his method of making the paths of electrically charged particles visible by condensation of vapour". http: //www. nobelprize. org/nobel_prizes/physics/laureates/1927/index. html

Promoting physics, supporting physicists More Nobel Prizes… The Nobel Prize in Physics 1948 The Nobel Prize in Physics was awarded to Patrick M. S. 1936 was divided equally Blackett "for his development of between Victor Franz Hess and Carl David Anderson "for the Wilson cloud chamber their discovery of the positron" method, and his discoveries which they photographed in a therewith in the fields of nuclear physics and cosmic radiation". cloud chamber.

Promoting physics, supporting physicists Making a Cloud Chamber

Promoting physics, supporting physicists Making a Cloud Chamber 1. Cut a 2 cm wide length of felt about 1 m long. 2. Stick to the “bottom” of the plastic fish tank. 3. Cut the lid of the fish tank. 4. Put tape along the slots left in the lid. 5. Tape the baking tray to the lid.

Promoting physics, supporting physicists You will need: A fish tank A baking tray Scissors Saw Snips Tape Metre stick Access to the roll of felt A marker pen

Promoting physics, supporting physicists You are going to stick felt around the “bottom” of the fish tank Mark two 2. 5 cm wide bands the width of the roll of felt and cut them off. Then cut these two strips so that you have pieces that fit the ends and sides of the tank.

Promoting physics, supporting physicists Peel the backing off the felt and stick it in place in the “bottom” of the fish tank.

Promoting physics, supporting physicists You're going to cut out the central part of the “lid” that is inside the lip.

Promoting physics, supporting physicists You should end up with something like this:

Promoting physics, supporting physicists Cover the slits along the sides with tape:

Promoting physics, supporting physicists Stick the lid to the baking tray with more tape:

Promoting physics, supporting physicists Put it all together:

Promoting physics, supporting physicists Using the Cloud Chamber • 1. Soak the felt in the chamber with Isopropyl alcohol. • 2. Get blu tac and a source and put them at one end of the cloud chamber. Use the blu tac to have the source about 5 mm above the base. • 3. Put dry ice in a tray. (With gloves). • 4. Put the cloud chamber on the dry ice. • 5. Arrange the lighting so trails will be lit from the side.

Promoting physics, supporting physicists What do you see? The tracks from beta can be observed, but they are much fainter; low-energy beta emissions produce very irregular tracks. Another way to identify beta tracks is to take a number of photographs at 1 second intervals with a digital camera and flash, say 10 or so, and then download the images to a computer. Zoom in on the photographs and with luck you may be able to pick out some images that show beta tracks. The contrast may be better if the pictures are changed to greyscale. Mostly alpha

Promoting physics, supporting physicists • A straight track that sharply "kinks" off to the left or right. This is a decay of a muon particle. The two dashed lines are particle called neutrinos that your chamber is not able to detect. • Three tracks that meet at a single point. In these events, one track is an incoming cosmic ray, a particle called muon. This particle hits an atomic electron. The electron and the outgoing cosmic track are the two other tracks. • A very windy, chaotic track. This is "multiple scattering", as a low-energy cosmic ray bounces off of one atom in the air to the next.

Promoting physics, supporting physicists Welding Electrode sources http: //www. practicalphysics. org/go/Apparatus_2298. html Welding Electrode Tungsten rod with 2% Thorium 232. Weakly radioactive. No special precautions required. Do not break or grind.

Promoting physics, supporting physicists Where to get dry ice • Online or by phone: http: //www. dryiceuk. com 0800 0842 040 http: //www. chillistick. co. uk/ 08433 192 919 http: //www. boconline. co. uk 0800 111 333 • Around £ 60 for 20 kg. They don't deliver on Mondays. • Or ask at pharmaceutical suppliers, airport food companies, universities. • • •

Promoting physics, supporting physicists Make your own Comet! http: //www. practicalphysics. org/go/Experiment_1039. html

Promoting physics, supporting physicists Apparatus and materials • Large polythene sheet to protect floor • Mixing bowl • Bin-liner bag, to line bowl and draw comet together • Mallet, to crush some dry ice to powder • Substantial plastic bag, in which to crush dry ice • Gardening gloves (heavy duty type) • Mixing spoon • Balance, to find mass of comet (and hence calculate a hypothetical kinetic energy) For two comets • Dry ice pellets, 10 kg • Garden sand, 1 kg • Water, 2 litres • Soil, 1 handful (organic constituent) • Worcestershire sauce (organic constituent) • Smelling salts (organic constituent) Technical notes The essential ingredients are dry ice, sand water. The other items represent the organic molecules thought to be present in a comet. If it feels as if the comet will not bind into a 'snowball', it is because you have not used enough water. There is a natural tendency not to want to use too much water for fear of evaporating all the dry ice.

Promoting physics, supporting physicists Teaching Radioactivity http: //www. iop. org/education/teacher/resources/radioactivity/page_41558. html