Malus’ Law

This section is part of the HSC Physics syllabus Module 7: Nature of Light under Light, the Wave Model. Malus’ Law is a fundamental principle in optics that describes the relationship between the intensity of light that passes through a polariser and the angle between the polariser and the direction of the incoming light.

The law states that the intensity of the light that passes through a polariser is proportional to the square of the cosine of the angle between the polariser and the direction of the incoming light.

To understand Malus’ Law, it’s helpful to think about the behaviour of light when it passes through a polariser. A polariser is a device that allows light to pass through it in only one direction. This means that light passing through a polariser will have a polarisation direction that is aligned with the orientation of the polariser.

If the polariser is positioned at an angle of 0° to the direction of the incoming light, the light will pass through the polariser at its maximum intensity. As the angle between the polarizer and the direction of the incoming light increases, the intensity of the light that passes through the polarizer decreases according to the square of the cosine of the angle.

Malus’ Law has numerous practical applications in various fields such as polarimetry, optics, and technology. It provides a means of analysing and explaining the behavior of polarised light, and it’s often used in conjunction with other optical principles to study light and electromagnetic waves.

In conclusion, Malus’ Law is a crucial concept in the study of optics and provides a simple and straightforward method of understanding the relationship between the intensity of light that passes through a polariser and the angle between the polariser and the direction of the incoming light. This law has far-reaching implications for fields such as technology and optics and is an essential aspect of the study of light and electromagnetic waves.