Polarising Sticky Tape

1. Polarising Sticky Tape Matthew Lam, Charling Li And JasjitManpotra

2. Aim • The aim of this experiment was to investigate the phenomenon that light passing through two polarising filters with sticky tape in between would appear as a mosaic of colours.

3. VARIABLES • Layers of sticky tape (investigated) • Alignment of overlapping sticky tape (investigated) • Orientation of polaroid lenses upon each other (investigated) • Alignment of sticky tape with the polaroid lenses (investigated) • Which lens the sticky tape is stuck on (kept constant) • Angle at which white light is entering the lenses (kept constant) • Angle at which exiting light is viewed (kept constant)

4. MATERIALS • Sticky Tape • 2 Polaroid lenses • LCD Screen • Camera • Scissors

5. Theory • Light is composed of two components perpendicular to each other. For natural white light, these components can be orientated in many directions. • When natural white light passes through a polarising filter, it becomes linearly polarised. When polarised light passes through a half wave plate, a phase difference of half a wavelength occurs. • The plane of polarisation will be rotated by twice the angle between the plane of polarisation and the axis of the half wave plate. • Half wave plates are made of birefringent materials, such as sticky tape. • Birefringent materials will cause light rays to split into the fast and slow ray. • This causes interference colours.

6. METHOD • Filter orientation – with just two pieces of tape on the filter, rotate it in front of the LCD, trying to keep it in on the same plane as the LCD • Sticky tape to filter orientation – place the tape on the filter at four different angles to the filter, whilst keeping the other variables constant. • Sticky tape to tape orientation – overlap two pieces of tape at three different angles whilst keeping other variables constant • Layers of tape – Adhere 8 pieces of tape directly on top of each other.

7. Results • Filter orientation • Layers of sticky tape • Sticky tape – filter orientation • Sticky tape – tape orientation

8. Discussion • All of the investigated variables had an effect on the colour observed. The greatest variety of colours is caused by the orientation of overlapping pieces of sticky tape, but the orientation of polarising filters is key to seeing the colours created. • This is because the sticky tape rotated each colour by certain degrees depending on their wavelength, thereby determining the colours created and the second filter only lets colours with the right orientation through, thereby determining the colours seen. • On the side, we also had quick study of the other variables that we mentioned earlier, and confirmed that they do affect the colour observed.

9. References • Heinemann Physics Year 11 textbook • http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html • http://demonstrations.wolfram.com/CircularAndEllipticPolarizationOfLightWaves/ • http://miniphysics.blogspot.com/2010/12/circular-polarization-by-quarter.html • http://www.physicsclassroom.com/class/light/u12l1e.cfm • http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html • http://www.meadowlark.com/applicationnotes/basic%20polarization%20techniques%20and%20devices.pdf • http://www.tulane.edu/~sanelson/eens211/interference_of_light.htm