• # question_answer 53) In the arrangement shown ${{L}_{1}},{{L}_{2}}$ are slits and ${{S}_{1}},{{S}_{2}}$two independent sources on the screen, interference fringes A)  Will not be thereB)  Will not be there if the intensity of light reaching the screen from ${{S}_{1}}$ and ${{S}_{2}}$ are equal.C)  Will be there under all circumstancesD)  We will have only the central fringe

On the screen, we have four amplitudes pair wise coherent. $({{A}_{1}}+{{A}_{2}})+({{A}_{3}}+{{A}_{4}})={{A}_{12}}+{{A}_{34}}$ However, if ${{A}_{12}}$ and ${{A}_{34}}$ have equal magnitude because of random phase of ${{A}_{12}}$ and ${{A}_{34}},$ no fringes will be seen.