# Can a Polarizer Change the Polarization State of a Laser Beam?

• james walshe
In summary, the conversation discusses the effects of polarization on a laser beam incident on a single polarizer. It is determined that if the laser beam is linearly polarized and aligned with the polarizer, 100% of the beam will be transmitted according to Malus's Law. If the beam is circularly polarized or randomly polarized, only 50% will be transmitted. It is also noted that a polarizer can change the orientation of the polarized beam, but not the polarization state.
james walshe
Hi there all,
I am a little confused about polarization. If I have a laser beam incident on a single polariser, if I adjust the angle of the polarizers transmission axis so that it is aligned with the plane of polarization of the incident laser beam does it intensity remain unchanged, or does it lose 50% of its intensity due to Malus's Law?. Also can a polarizer change the polarisation state of the incident beam or will the transmitted beam always be linearly polarised?.

Hi, welcome to PF.

If the laser beam is linearly polarized, and it's an ideal polarizer, then 100% of the beam is transmitted when the laser polarization is aligned with the polarizer -- in accordance with Malus's Law:

$$\frac{I}{I_{inc}}= \cos^2 \theta \text{, with } \theta=0$$

If the laser beam is circularly polarized or randomly polarized, then 50% is transmitted.

Also can a polarizer change the polarisation state of the incident beam or will the transmitted beam always be linearly polarised?
The transmitted beam will remain linearly polarized, but change in orientation, as the polarizer is rotated.

Hope that helps.

Last edited:
1 person

## What is polarization?

Polarization is a phenomenon in which a light wave is restricted to vibrate in a specific direction. This means that the electric field of the light wave is confined to a single plane.

## What is Malus's Law?

Malus's Law is a mathematical equation that describes the intensity of light after passing through a polarizer. It states that the intensity of polarized light is proportional to the square of the cosine of the angle between the polarizer and the light's original direction of polarization.

## How does Malus's Law explain the behavior of polarized light?

Malus's Law helps us understand how polarized light behaves when it passes through a polarizer. The law states that the intensity of polarized light decreases as the angle between the polarizer and the light's original direction of polarization increases. This is because the polarizer only allows light waves that are aligned with its transmission axis to pass through, blocking all others.

## What are some examples of polarized light in everyday life?

Polarized light is commonly seen in sunglasses, as they reduce glare by blocking horizontally polarized light reflected off of surfaces such as water or roads. Polarized filters are also used in cameras and 3D glasses to enhance image quality and create the illusion of depth, respectively.

## What are the applications of polarization and Malus's Law in science and technology?

Polarization and Malus's Law have a wide range of applications in science and technology. They are used in various fields such as optics, astronomy, and telecommunications. Some specific applications include polarizing microscopes for studying crystals, polarized light therapy for treating certain skin conditions, and polarization imaging techniques for detecting cancerous tissues.

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