Ordinary light is (a) plane polarised (b) circularly polarised (c) alliptically polarised (d) unpolarised

To answer your question about the nature of ordinary light, the correct choice is (d) unpolarised. Let’s delve into what this means and why ordinary light is classified this way.

Understanding Light Polarization

Light is an electromagnetic wave, and it can oscillate in various directions. When we talk about polarization, we're referring to the orientation of these oscillations. In simple terms, if light waves vibrate in a single plane, they are considered polarized. If they vibrate in multiple planes, they are unpolarized.

Characteristics of Ordinary Light

Ordinary light, such as sunlight or light from a bulb, consists of waves that vibrate in many different directions. This randomness in the orientation of the light waves is what makes it unpolarized. Here’s a breakdown of the types of polarization:

• Plane Polarized Light: This type of light has waves oscillating in a single plane. It can be produced using polarizing filters.
• Circularly Polarized Light: In this case, the light waves rotate in a circular motion as they propagate. This is often used in 3D glasses.
• Elliptically Polarized Light: This is a more general form of polarization where the light waves describe an ellipse. It can be thought of as a combination of linear and circular polarization.
• Unpolarized Light: As mentioned, this is the typical state of light, where the waves vibrate in multiple planes.

Examples and Applications

To illustrate, think about how polarized sunglasses work. They contain a special filter that blocks certain orientations of light waves, reducing glare from surfaces like water or roads. This is effective because the sunlight that reflects off these surfaces often becomes polarized, while the light coming directly from the sun remains unpolarized.

In summary, ordinary light is unpolarized because it consists of waves vibrating in multiple planes. Understanding this concept is crucial for various applications in optics, photography, and even in technologies like LCD screens, which utilize polarized light for better image quality.