Describe briefly, with the help of suitable diagram, how the transverse nature of light can be demonstrated by the phenomenon of polarization.
Experiment to prove transverse nature of light waves:
T1 and T2 are two tourmaline crystals cut with their faces parallel to the crystallographic axis. Light from a source is passed through the crystal T1. If the crystal T1 is rotated with the incident light direction as axis from 0 to 360°, the transmitted light will show no variation in intensity.
Now the crystal T1 is kept fixed. The second crystal T2 whose axis s parallel to T1 is rotated about the incident beam.The light transmitted by the crystal T2 shows a variation in intensity when it is rotated.The intensity of transmitted beam becomes zero when the axis of both the crytals are at right angles to each other.If crystal T2 is rotated further the intensity increases and reaches a maximum when the axis of two crystals are parallel to each other.
When the axes of the crystals T1 and T2 are parallel , the light transmitted by the crystal T2 is maximum.When they are perpendicular to each other the light transmitted by the second crystal is zero. The crystal T1 is called the polariser and the crystal T2 is called the analyser.
This experiment shows that light waves are transverse in nature.If light waves were longitudinal, then the light transmitted by the crystal T2 would not have shown any variation in intensity when it is rotated.