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In a double slit experiment, the distance between the slits is 3 mm and the slits are 2 m away from the screen one due to light with wavelength 480 nm, and the other due to light with wavelength 600 nm. What is the separation on the screen between the fifth order bright fringes of the two interference patterns ?



β= λD/d                                                                                                (1/2) marks

   5th bright = 5β1=5λ1D/d=5×480×10-9 ×2/3×10-3=16×10-4 m    (1) marks 

   5th bright = 5β2=5λ2D/d=5×600×10-9 ×2/3×10-3=20×10-4 m    (1) marks

    distance between two 5th bright frings =(20-16) ×10-4 =4×10-4m     (1/2) marks