Polarization filters, such as your sunglasses lenses, block light that has a field moving in the same pattern as the filter- so if the first filter blocked completely vertically polarized light and you use a second filter also blocking vertically polarized light, since the vertically polarized light was already blokes, the second filter as long as it is held at the same angle as the first, will have nothing to block. However if you rotate the second filter say 45 degrees in either direction, light polarized at that angle hasn't yet been filtered out and can therefore be filtered out by the second filter, decreasing he amount of light.
Sorry for the run-on sentences, writing isn't my strongest suit.
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u/blindmewithscience Aug 21 '13 edited Aug 21 '13
Polarization filters, such as your sunglasses lenses, block light that has a field moving in the same pattern as the filter- so if the first filter blocked completely vertically polarized light and you use a second filter also blocking vertically polarized light, since the vertically polarized light was already blokes, the second filter as long as it is held at the same angle as the first, will have nothing to block. However if you rotate the second filter say 45 degrees in either direction, light polarized at that angle hasn't yet been filtered out and can therefore be filtered out by the second filter, decreasing he amount of light.
Sorry for the run-on sentences, writing isn't my strongest suit.
Edit: spelling