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.2 a) A particular LED emits electromagnetic radiation of wavelength 940 nm with a linewidth of 40 nm. Find the frequency band width and the coherence length of this [4] source. b) P polarised light with wavelength 940 nm is incident at Brewster's angle on a block of material A which has refractive index 3.05. The block is partially submerged in a liquid with refractive index 1.35, as illustrated in image below left. All the incident intensity is transmitted through the block, into the liquid. (i) Calculate Brewster's angle for material A and find the transmission angle for the air-A boundary. (ii) Find the angle o, shown in image, that determines the orientation of the lower surface of the block. 0.4 2 08 0.35 0.3 n 0.25 0.2 0.15 -500 0 500 1000 1500 2000 2500 Time (seconds) air liquid A Reflectivity [3] [2]