# Physics q from isaac phys help ??

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In some crystals, light waves with different planes of polarisation travel at different speeds. A thin slice of a particular quartz crystal has a refractive index of 1.553 for light incident normally on the slice and polarised linearly in direction A, but 1.544 for light incident normally on the slice and polarised linearly in direction B, which is perpendicular to A.

For light of wavelength 535nm (in a vacuum), what is the minimum thickness of quartz that will introduce a 𝜋rad phase difference (a difference of half a wavelength over the same path) between the two polarisations?

I have attached my working and since you can't see the correct answer on isaac phys I don't know what to work towards and am finding this q very difficult.

Part B:
A wedge with an angle of 3.00∘, made with the same birefringent quartz, is placed between two polarisers with perpendicular polarisation directions. Monochromatic light of wavelength 695nm is shone through the setup.

The light emerging from the first polariser is polarised at an angle of 45∘ to A and so can be considered to be made up of equal amplitudes of light with polarisation directions A and B defined above. A phase difference of 𝜋rad (or a difference of half a wavelength over the same path) between the components of light of the two polarisations has the effect of rotating the plane of polarisation of this light by 90.0∘.

Bright bands are observed in the light transmitted by the second polariser. What is the horizontal spacing between two consecutive bright bands?

I don't even know where to begin with this part.
Last edited by Orss_; 7 months ago
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