White light reflected at normal incidence from a soap film has minima at 6500 Å and maxima at 7500 Å in the visible region with not minimum in between. If is 5 3 for the, thin film, the thickness of film is

Step-by-step solution

For minima to occur, 2 t=2 n ₁ 2 (i) and for maxima 2 t=(2 n-1) ₂ 2 (ii) From Eqs. (i) and (ii), we get (2 n-1) ₂=2 n ₁ or (2 n-1) 7500=(2 n) 6500 [given, ₂=7500 Å, ₁=6500 Å ] or 1500 n-7500=13000 n or 2000 n=7500 or n=3.75 Substitution the value of ( n ) in Eq. (i), we get 2 5 3 t=2 3.75 6500 2 10⁻¹⁰ [ = 5 3 ] t=7.40 10⁻⁷ ~cm