Conduct investigations quantitatively using the relationship of Malus’ Law
Hyugens’ model showed that light was a wave.
The phenomena of polarisation helped us understand that light was a transverse wave . A transverse wave has oscillations perpendicular to its direction of propagations. A polariser allows components of oscillations which are parallel to the axis of polariser.
The new lightwave with restricted plane of oscillations is called a Polarised Light
A polariser thus reduces the original intensity to half
If we pass the Polarised light through a second polariser, with a different axis of polarisation, then the final intensity is given by :-
, where
- I new : the intensity if the emerging polarised light
- I O : the intensity of polarised light falling on the second polariser
- θ = the angle between the axis of the incident polarised light and the axis of the second polariser
To conduct an investigation we would need :
- A light source
- 2 polarising filters
- a light sensor
- Darken the room, and use the light sensor to measure the light intensity produced by the light source
- Place one of the polarising filters in front of the light source and measure the intensity of the polarised light.
- Should be half of original. Refer to this as Io
- Place a second polariser and let the polarised light pass through it.
- Rotate the axis of the second polariser with respect to the first, and measure the intensity of the emerging wave for different angles .
The readings should verify Malu’s Law.
Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)