Polarisation and Malus’ Law – Practice


1) Polarised light with an intensity of 40cd passes through a analysing filter at an angle of 72° to the plane of the incident light. Calculate the intensity of the light as it passes through the polarising filter:

2) At what angle must an analysing filter be orientated at for the intensity of the light to be 50% of its original intensity?

3) A student placed two polarising filters together to reduce the intensity of light passing through them. They were originally placed at an angle of 10° and the student still wanted to reduce the intensity of the light. At what angle should the student place the analysing filter if they want the light intensity to be 1/5 of the intensity when the angle was 10°?

Quick Answers:

1) 3.82 cd

2) 45°

3) 63.9°

Worked Answers: