Question

A polariser is used for (A) produce polarised light (B) produce unpolarised light (C) produce unpolarised light (D) none of these

Short answer

A polariser is used primarily to produce polarised light by allowing light waves of a specific polarization to pass through while blocking light waves of other polarizations. Hence, the correct answer is (A) produce polarised light.

Step-by-step solution

Understanding the role of a polariser

A polariser is an optical filter that allows light waves of a specific polarization to pass through while blocking light waves of other polarizations. It has the ability to transform unpolarised light into polarised light or to filter the polarisation of already polarised light.

Analyze the given options

(A) Produce polarised light: Polarisers are used to transform unpolarised light into polarised light. This is one of their main applications. (B) Produce unpolarised light: Polarisers cannot produce unpolarised light. They can only filter polarisations. (C) Produce unpolarised light: This option is the same as (B) and is also incorrect. (D) None of these: This option is incorrect because polarisers are known to produce polarised light.

Select the correct answer

Based on our analysis, the correct answer to this exercise is (A) produce polarised light.

Key concepts

Polarised light

When light is polarised, its waves are aligned in a specific direction. This means that the light's electric and magnetic fields vibrate in a single plane, making it different from unpolarised light, which vibrates in all directions. An easy way to visualize this is to imagine that polarised light behaves like a series of tightly aligned strings, where all the strings move in the same direction.
Polarised light is commonly produced using a device called a polariser. A polariser functions to selectively allow light waves vibrating in a particular direction to pass through, while blocking others. This process is crucial in various applications, such as reducing glare from surfaces like water or glass, improving contrast in photography, or in 3D movie glasses.
Polarisers are vital components in many optical instruments and technologies. They help in controlling the intensity and direction of light, which can enhance visual clarity and reduce eye strain by filtering out unwanted orientations of light.

Unpolarised light

Unpolarised light is the type of light most people encounter in everyday life. Unlike polarised light, unpolarised light contains waves vibrating in multiple directions. A helpful analogy is to think of it as a ball of yarn with strands sticking out in every direction. This type of light can be found in natural states, such as sunlight or artificial light from bulbs.
By using a polariser, the unpolarised light can be converted into polarised light. When unpolarised light strikes a polariser, only the components of the light wave that are aligned with the polariser’s axis can pass through. The other components are absorbed or reflected, resulting in polarised light on the other side. This transformation is a key principle in a variety of technologies, from photography to liquid crystal displays (LCDs).

• Unpolarised light waves vibrate in all directions.
• Converted to polarised light by using polarisers.
• Commonly originates from natural and artificial sources.

Optical filter

An optical filter is a device that selectively allows certain wavelengths of light to pass while blocking others. In the case of a polariser, it acts as a special kind of optical filter. By filtering light based on its polarization, it enables applications that require controlled light conditions.
Optical filters are not limited to polarization alone. They can also manipulate light based on color or intensity. For instance, a color filter might only transmit blue light, while blocking red and green. This versatility makes optical filters essential in fields like photography, scientific research, and telecommunications.
In summary, optical filters, including polarisers, play a vital role in managing light properties. They allow for precise control over which parts of the light spectrum are utilized in specific scenarios, thus enhancing the capabilities and performance of many optical devices.