Question

What is a polaroid? State its two uses.

Answer 1

Hint: A polaroid is a device that allows only one half of the vibrations of the transmitted light to pass through the filter only in one plane. The resulting light that will emerge is known as polarised light. It is prepared artificially so as to obtain polarised light. The intensity of the polarised light will be different from unpolarised light.

Complete solution:
Step I: A polaroid is a type of plastic sheet that polarises the transmitted beam of light. The sheets of polaroid contain a long chain of molecules that allows the electric field oscillations to pass only in one direction. During filtration, the molecules of a polaroid are stretched across the filter. The plane through which the unpolarised light passes and emerges out as polarised light is known as plane of polarisation.
Step II: Uses Of Polaroids:
1. These are used in sunglasses so as to avoid glare of sunlight.
2. It is used to create 3D-motion pictures. This process is also known as holography.

Note: It is important to remember that the light wave is considered as the sinusoidal oscillation of the electromagnetic fields. These light waves are produced by vibrating electric charges. Since the electric and magnetic fields are perpendicular to the direction of the oscillation of waves, the only electric and magnetic fields that are in the plane of polarization will pass. Also the electric and the magnetic fields are perpendicular to each other. The direction of the electric field after polarisation is known as the polarising direction.