CAIE A-Level Physics AS 7.5.2 Maluss Law I I0 Cos2 to Calculate the Intensity of a Plane Polarised Questions
Use Malus’ law and polarisation concepts to analyse intensity through polarisers.
- Syllabus
- 2028–2030
- Course
- Physics 9702
- Level
- AS
Use Malus’ law and polarisation concepts to analyse intensity through polarisers.
A beam of vertically polarised light is incident normally on a polarising filter, as shown in Fig. 5.1.
Fig. 5.1
The transmission axis of the filter is initially vertical. The filter is then rotated through an angle of 360∘ while the plane of the filter remains perpendicular to the beam.
On Fig. 5.2, sketch a graph to show the variation of the intensity of the light in the transmitted beam with the angle through which the transmission axis is rotated.
Fig. 5.2
light intensity has maximum value at 0∘,180∘,360∘ and zero intensity at 90∘,270∘
'sinusoidally-shaped' curve
The intensity of the light in the incident beam is 7.6Wm−2. When the transmission axis of the filter is at angle θ to the vertical, the light intensity of the transmitted beam is 4.2Wm−2.
Calculate angle θ.
4.2=7.6cos2θθ=42∘