KCET2010PhysicsWave Optics
What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film =1.5 , wavelength of the light incident on the film =600 ~nm .
Options
- A100 ~nm
- B300 ~nm
- C50 ~nm
- D200 ~nm
Correct answer
A. 100 ~nm
Step-by-step solution
Condition for constructive interference is 2 t =[2 n +1] 2 where, n =0,1,2,3 For minimum thickness, n =0 gathered 2 t = 2 t = 4 = 600 10⁻⁹ 4 1.5 =100 ~nm gathered