answer pls

3: (a) (i) You are called as an expert witness in a trial. The defendant is accused of stealing information by reading a printed document that was pinned to a wall 50 m away. The defence says this is impossible but the prosecution has demon- strated that the defendant has extremely good eyesight. What testimony would you give? You should assume the writing was similar in size to the printing on this exam paper, and your answer should be supported by physical arguments and a calculation. (ii) The prosecution now alleges that the defendant stole the information by taking a picture (from the same distance) with his mobile phone camera at high zoom. The lens of the camera has a diameter of 2 mm. Would your testimony change? Explain briefly. (b) You need to buy a diffraction grating for a spectrograph that must be able to resolve the sodium doublet (588.995 nm and 589.592 nm). The gratings in the catalogue are 20.0 mm wide and are blazed to work in first order. Grating A has a groove spacing of 30 lines per mm and Grating B has a groove spacing of 60 lines per mm. Which grating should you choose? Justify your answer with a calculation. (10 marks)