A plane wave of monochromatic light falls normally on a uniform thin layer of oil which covers a glass plate. The wavelength of source can be varies continuously. Complete destructive interference is observed for\[\lambda =5000\overset{o}{\mathop{A}}\,\] and \[\lambda =1000\overset{o}{\mathop{A}}\,\] and for no other wavelength in between. If \[\mu \] of oil is 1.3 and that of glass is 1.5, the thickness of the film will be

A plane wave of monochromatic light falls normally on a uniform thin l

1.	A plane wave of monochromatic light falls normally on a uniform thin layer of oil which covers a glass plate. The wavelength of source can be varies continuously. Complete destructive interference is observed for\[\lambda =5000\overset{o}{\mathop{A}}\,\] and \[\lambda =1000\overset{o}{\mathop{A}}\,\] and for no other wavelength in between. If \[\mu \] of oil is 1.3 and that of glass is 1.5, the thickness of the film will be
A.	\[6.738\times {{10}^{-5}}cm\]
B.	\[5.7\times {{10}^{-5}}cm\]
C.	\[4\times {{10}^{-5}}cm\]
D.	\[2.8\times {{10}^{-5}}cm\]
Answer» B. \[5.7\times {{10}^{-5}}cm\]