question_answer

A double slit \[{{S}_{1}}-{{S}_{2}}\]is illuminated by a coherent light of wavelength\[\lambda \]. The slits are separated by a distance d. A plane mirror is placed in front of the double slit at a distance \[{{D}_{1}}\]from it and a screen \[\Sigma \]is placed behind the double slit at a distance \[{{D}_{2}}\]from it (Figure). The screen \[\Sigma \]receives only the light reflected by the mirror. Find the fringe-width of the interference pattern on the screen in mm. \[({{D}_{1}}=1meter,\,\,{{D}_{2}}=2\,meter,\,\,\lambda =1000~\overset{\text{o}}{\mathop{\text{A}}}\,,\text{ }d=0.1mm)\]

Answer:

4.00