Question

Distinguish between unpolarized light and linearly polarized light. How does one get linearly polarized light with the help of a polaroid.

Answer 1

Hint: The magnetic field and electric field exist in the electromagnetic wave and light is also an EM wave and the direction of propagation of light and oscillations of magnetic field particles and electric field particles are mutually perpendicular. We differentiate polarized and unpolarized waves based on the direction of oscillation of the electric field.

Complete answer:
There are two kinds of waves normally. One will be a transverse wave and the other will be a longitudinal wave. If we consider transverse waves, the propagating particles vibrate ninety degrees to the direction of propagation. Transverse wave has crests and troughs. In case of the longitudinal wave the propagating particle usually executes vibration in the same direction of wave propagation. This longitudinal wave has compressions and rarefactions. In case of longitudinal waves particles vibrate in to and fro motion. Transverse waves can propagate without medium too whereas longitudinal waves require medium to propagate. One of the examples of transverse waves is light and sound is a longitudinal wave.
In case of unpolarized light the direction of oscillations of electric and magnetic fields are always mutually perpendicular in all the directions and in all the planes. In case of linearly polarized light the direction of oscillation of electric field will be only along one direction, I.e only in one plane.
With the help of polarizer there will be transmission axis and electric field will oscillate only in one plane along the transmission axis. In this way polaroid is used to linearly polarize light.

Note:
Light is an electromagnetic wave which is transverse in nature where the phase of the magnetic field and the electric field will be the same for this EM wave. Light carries energy in the form of small packets called photons. The velocity of photons will be the same as the velocity of light.