Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
Physics Experiments at
the 2014 ASE
Conference
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
FIRE PISTON
The Hyman Fire Piston demonstrates the large rise in temperature, when a fixed mass of gas is
compressed quickly. This phenomenon is apparent when a bicycle pump warms up, when
inflating tyres. The principle is used to ignite the fuel in a diesel engine.

Use a thick felt pad between your hand and the piston knob to avoid hurting
your hand.

Ensure that the flexible plastic sleeve is over the combustion end of the cylinder
during compression

Do not use the unit if there is any sign of damage to it
(eg the acrylic tube is cracked)
1. Take a small sample of cotton wool and spread the fibres
out, to allow more air to reach the wool.
2. Use a small stick to push the sample of cotton wool a cm or
so into the protected end of the tall acrylic cylinder.
3. Gently slide the acrylic cylinder over the O-ring on the steel
spiggot on the base; avoid crushing the cotton wool too
much or damaging the O-ring.
4. Carefully insert about 2cm of the steel piston into the open
end of the cylinder. A small smear of lubricant may enable
smoother movement.
5. Use a thick felt pad on top of the black knob and place the
palm of your hand on top.
6. Watch the cotton wool carefully…
7. Keep the piston vertical and push it down as fast as you can.
The cotton wool should ignite.
8. Let the burned product cool down.
9. Pull the piston up rapidly and you may see water vapour
condense inside, as the pressure decreases and the
temperature falls.
The Hyman Fire Piston costs about £30 and is available from
many science education suppliers,
www.cochranes.co.uk
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
MAGDEBURG HEMISPHERES
You could choose the apparatus used in the scene below.
The experiment was performed in 1657 at Magdeburg, Germany by Otto von Guericke (16021686), the Burgomeister (mayor) of Magdeburg.
But why not take the heavy work out of this demonstration with plastic hemispheres
and a hand held vacuum pump? See CLEAPSS leaflet PS83 for more details.
Plastic hemispheres from suppliers including
www.timstar.co.uk
JN, Jan 2014
Gunson 77003 pump, about £50 from
www.gunson.co.uk or www.amazon.co.uk
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
RADIOACTIVIVE URANIUM (VASELINE) GLASS
Uranium (vaseline) glass was so named because of is resemblence in colour to vaseline petroleum
jelly. In the mid 19th and early 20th Century, various domestic items of glassware were coloured
various shades yellow/green using uranium compounds. Uranium-238 has a half life of 4500000000
years (4500 million years), so these items are usually still radioactive!
Check the range of the radiation and put some absorbers between the vase and the GM
tube to see if you can work out which radiation(s) may be present.
Uranium glass ornaments are often available on E-Bay, from charity shops and may be
found in elderly relatives’ possessions (please ask before “borrowing”).
The “domestic” ornament used here is of very low radioactivity and poses no risk to health
(unless you drop it, break the glass and cut yourself – hence the special control measure!)
You should refer to CLEAPSS guide L93 model risk assessment 14 for
more information on this type of low-level radioactive source
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
LASER RAY BOX
Semiconductor lasers are widely available in domestic and educational markets.
CLEAPSS advice is to purchase lasers for use in school only from scientific educational
suppliers.
The Rayzer Lightbox from DJB Microtech is one example of such a product.
Its safe use must be managed carefully.
See CLEAPSS leaflet PS52 for more information and safety advice on lasers.
You will need
RayZer lightbox fixed to baseboard
9V dc plugtop supply
Sheets of A4 plain paper
Set of Prisms, Lenses and Mirrors
LASER RADIATION
Warning do not stare into the beam.
This class 2 laser product will not harm the eyes, if viewed briefly by accident.
The power is similar to that used in supermarket product scanning.
Ensure that beams shine towards a wall and never towards people’s eyes.
The Rayzer light box costs about £70.
The sectional lenses cost about £35.
www.djb.co.uk
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
COLOUR MIXING
The increased brightness and falling cost of light emitting diodes means that several suppliers
are now offering very effective colour mixing equipment, such as this red green and blue
adjustable brightness unit, made by www.electrosound.co.uk
Test out the unit provided using the photographs below as a guide for getting best results.
additive colour mixing
complementary colour mixing
Try altering the relative brigtness of the LEDs for different effects and any other investigation
you can think of. Avoid staring into the bright LEDs and do not shine them at other people.
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
BROWNIAN MOTION USING A LASER SMOKE CELL
DRAFT
An updated version of this profound experiment, the laser smoke cell uses a low power red
laser to illuminate the smoke particles, which can be observed using a microscope. It is a lot
easier and quicker to setup this experiment compared with the Whitley Bay smoke cell.
http://www.timstar.co.uk/Item/Science_Supplies~BRANDS~Fredriksen/HE53652/LASER_SMOKE_CELL.html
DRAFT
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
MAKE YOUR OWN SPECTROMETER
Introduction – why do this
Observing line spectra is an important part of studying physics and chemistry. All elements absorb and
emit light of characteristic wavelengths, which appear as coloured lines when viewing a sample of an
element through a diffraction grating. Line spectra act as an ‘atomic fingerprint’, with each element
having its own unique spectrum.
You will need:
 Plastic tubing no more than 2.5 cm in diameter
 Hacksaw
 Diffraction grating
 A mobile phone and protective case ( the case is optional)
 Black insulation tape
 Things to look at (gas discharge tubes, flame tests, different coloured light sources, LEDs etc)
Cut your tube so it is 5-8 cm in length. If you
have used plastic piping or a plastic syringe
then sand down or file the edges so they are
smooth.
Feed lengths of the black insulation tape
through the tube, keep doing this until the
entire of the inside in covered in black tape.
You may wish to cover the outside of your
spectrometer to make it more aesthetically
pleasing.
Using 2 small strips of black insulation tape,
create a narrow (should be less than 1mm) slit
across the diameter of one of the openings.
Ensure this slit is across the centre of the
opening, as shown in the picture.
Tape a diffraction grating (the one we tested
was 1000 lines per mm) over the lens of the
phone. Some lenses protrude and you may
scratch the plastic lens cover so use a
protective phone case if you have one. Then
tape the open end of the tube over the phone
lens/diffraction grating, making sure that the
slit and the diffraction grating lines are parallel
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
to each other.
Open the camera app and point your
spectroscope at anything which emits light. If
you see nothing then you may have to wriggle
the scope around to ensure it is in line with the
lens and whatever you are observing.
These are pictures of various emission spectra
taken with our home-made spectrometer.
What to look at
 Emission spectra of gas discharge tubes
 Different colours on a computer monitor or data projector to see their component colours (use
the fill tool within Microsoft Paint)
 RGB matrix of a TV/Monitor
 Incandescent light source (e.g. filament bulb) will give a continuous spectra
 Flame tests e.g. lithium chloride
The science behind this activity
Each element has electrons which inhabit energy levels. Each element has its own set of discrete
energy levels. When light is incident upon a given element, electrons absorb certain wavelengths, or
colours of the light. This absorption spectrum has black lines at specific places in the spectrum. When
the excited electrons revert to a lower state, they re-emit this light producing an emission spectrum.
A narrow slit allows a thin strip of light through, which when it hits a diffraction grating it is split into its
constituent colours. Different colours are diffracted by different amounts as per the equation:
sin
λ
Where d = the distance between two slits on the diffraction grating, θ=the diffraction angle, n = the
‘order’ of maxima (always an integer), and λ = the wavelength of light. This means that red light (which
has a longer wavelength) is diffracted more than blue light.
Continuous spectrum: white light split is
into its constituent wavelengths.
Emission spectrum from electrons deexciting from excited energy states.
Absorption spectrum from electrons
absorbing specific frequencies of light,
moving them to higher energy states.
A common question – “Surely in an absorption spectrum the electrons will ‘fall’ back to the lower
energy state almost immediately re-emitting the energy they absorbed and so filling in the dark bands?”
The electrons do indeed ‘fall’ back to the lower energy state almost instantaneously re-emitting the
energy they absorbed (as per the emission spectrum) however the re-emitted light is emitted equally in
all directions (360o sphere) and so only a tiny fraction is emitted in the direction of the original beam of
light giving rise to the dark lines.
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Annual Conference CLEAPSS Physics investigations
Please ask if you are unsure or need help
MOBILE PHONE MICROSCOPE
This document tells you how to convert your smart
phone into a microscope camera to take extremely
close pictures of objects which cannot be seen easily
with the naked eye. The lens used is a focusing lens
from a laser pen/pointer.
You will need:
 A laser pointer
 A mobile phone
 Vice and pliers
Either buy a laser module, or remove one from a laser
pen. They come in all sorts of shapes and sizes so
you may want to buy a selection.
The bottom section (arrowed in the photo) unscrews
off, you may have to remove some stickers on the
case first.
Warning do not switch the laser on (See CLEAPSS
guide PS 52 for advice on the safe use of lasers in
schools)
Once unscrewed, you are left with the laser diode.
This is in two parts, one of which contains the laser
focusing lens we need for our macro lens.
Clamp the bottom half of the laser diode, and use a
pair of pliers to unscrew the top half. Be careful not to
use too much pressure because you may put a lot of
stress on the lens inside and may shatter it.
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk
Once the lens housing is removed, use a blunt pencil,
to push the lens out.
Attach the lens to a hairpin, and place it directly on
top of your smart phone’s camera lens. Tape the
hairpin down with sellotape. If the phone has an LED
flash, then ensure that it is not covered with the tape
as it comes in handy when taking pictures.
Position of hairclip under tape
Take pictures! You have to get really close, as the focal length of the lens is very small.
Experiment with and without the flash. Below are some of the pictures we took with our macro
lens. It is possible to take video clips too; an example would be of group 1 metals tarnishing in
air.
From top left to bottom right: ballpoint pen, compound eye of a wasp, RGB matrix of ‘white’ on a
monitor, salt, Queen’s eye on £10 note, matchstick, mm divisions on a ruler, compound eye of a
woodlouse, component on PCB.
JN, Jan 2014
© CLEAPSS, The Gardiner Building, Brunel Science Park, Kingston Lane, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: science@cleapss.org.uk; Web site: www.cleapss.org.uk