Polaroid is made of natural tourmaline crystal but the large size tourmaline crystal occurring naturally are not available, hence, tourmaline is not suitable for large size light polarization. Therefore, in practice artificial Polaroid is used which is made from herapathite crystals which are packed side by side, in layers with their axis parallel.
Consider the following figure.
When polaroid T1 is rotated about the axis of the direction of the propagation of light, the intensity of the transmitted light remains the same. Slowly when T2 is rotated, the intensity decreases and the transmitted light vanishes completely when T2 is perpendicular to T1. This is because the polaroid allows only those vibrations of light to pass through it which are parallel to its axis. This is true only if light has vibrations in all the directions and hence is a transverse wave.
Light waves are transverse waves hence; they have electric vectors in all possible directions. When a polaroid is placed between the path of the light, the electric vectors which are parallel to the pass-axis of the polaroid will pass through it. If the polaroid is rotated in any direction, there will be other electric vectors which are parallel to pass- axis and hence, will pass through it. So, the intensity of light does not change with respect to the orientation of pass-axis of the polaroid.
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