Question
Explain polarisation of light.
✓
Answer
When ordinary light emerges through the tourmaline crystal plate $P_1$, its nature is not the same as it was before entering $P_{1}$, because now when the plate $P_{1}$ is rotated about the direction of transmission of light, there is a change in the intensity of the light emerging from it. It happens. When the axes of both the crystals are parallel to each other, then the intensity of the output light is maximum [Fig. (a)]. From this position, when $P_{2}$ is roatated around the direction of light transmission, the intensity of the emitted light decreases and when the axes of both the crystals are perpendicular to each other, no light is emitted [fig. (b)]. It is clear from this that the light emitted from $P_{1}$ is not symmetric about the direction of light transmission, its vibration are limited to a plane normal to the direction of transmission. This light is called polarized light and this phenomenon is called polarization of light.
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