A parallel beam of light of 500nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1m away. It is observed that the first minimum is at a distance of 2.5mm from the centre of the screen. Calculate the width of the slit.
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The distance of the nth minimum from the centre of the screen is, xn=nDλa Where, D= distance of the slit from the screen λ= wavelength of the light a= width of the slit For first minimum, n=1 Thus, 2.5×10−3=(1)(1)(500×10−9)am a=2×10−4m a=0.2mm