1. (a)Distinguish between Fraunhofer and Fresnel diffractions. (5 marks) (b) Parallel rays of light with wavelength λ =

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1. (a)Distinguish between Fraunhofer and Fresnel diffractions. (5 marks) (b) Parallel rays of light with wavelength λ = 500 nm are incident on a slit of width a = 0.2 mm. A diffraction pattern is formed on a screen at a distance D=2.5 m from the slit. Find the position of the first minimum and the width of the central bright fringe. (2.5 marks) (c) White light containing wavelengths from 400 nm to 750 nm strikes a grating containing 4000 slitscm-¹. Determine that the blue light, λ = 450 nm of the third-order spectrum overlaps the red light, λ = 700 nm of the second order. (3 marks)