question_answer

Two coherent narrow slits \[{{S}_{1}}\] and \[{{S}_{2}}\]emitting light of wavelength \[\lambda \]in the same phase are placed parallel to each other at a small separation of\[3\lambda \]. The light is collected on a screen S which is placed at a distance\[D(>>\lambda )\] from the slit \[{{S}_{1}}\] and shown in figure. The distance x such that the intensity at point P is equal to the intensity at O is\[\frac{D}{2\sqrt{5}}\times a\]. Find the value of\[a\].

Answer:

5.00