Students investigate how well the various properties of light can be matched to the behavour
of particles and then waves.
Particle model of light apparatus, Laser and IEC Laser Optics Show (available from IEC Australia), S
lide of single slits, 2 polaroid filters, IEC diffraction kit and 2-12 V AC/DC power supply
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Young's Experiment
In this experiment a laser is aimed at a double slit. The light is allowed to pass into the Optical
Laser show (IEC Australia) The nodes and anti nodes of the interference pattern can be seen as
stripes in the mist that is sprayed into the Laser Show. The interference pattern is then
projected onto a screen and the wavelength of the laser light is calculated from the appropriate
measurements. The effect on the interference pattern of changing the wavelength and the slit
separation is investigated.
Laser and IEC laser optics show, IEC diffraction kit and 2-12 V AC/DC power supply,
Slide of double slits, Screen, 1 metre rulerTop
Energy of Electromagnetic Waves
In this experiment students investigate the photoelectric effect by first investigating the discharge of a positively and negatively charged electroscope with different metals on its cap when light and UV light are shone on it. They then perform an experiment using the apparatus available or analysye the results of Robert Miliken's Photoelectric effect experiment and discover the equation that calculates the energy of an individual photon. Planck's constant, threshold frequency and the Work Function are defined. Students discover how to use the number 12397 to convert energies of photons in eV to wavelengths in Angstrom units. The use of the photocell in producing movies with sound is discussed.
Electroscope, Plastic and ebonite rods, Plastic sheet and woollen cloth, 240 V light globe or Ray/light
Box, Ultra-violet light source, Copper and zinc plates and steel wool to clean them, Photoelectric effect
apparatus, Mercury vapour lamp Top
This is the Grand Finale! Students use the knowledge they have acquired during two years of
study to calculate the energy levels of the electron orbiting the hydrogen atom using the
standing wave model for the electron. They then predict the colours of the Balmer series of
lines in the hydrogen emission sprectrum. They check their predicton by viewing a spectrum
with a spectroscope. "That's amazing - we just drew those colours on our sheets is a typical
reaction from a student!"
Induction Coil, Hydrogen discharge tube, Spectroscope, 0-12 V DC supply
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