COMEDK2020PhysicsWave Optics
A plastic sheet (refractive index =1.6 ) covers one slit of a double slit arrangement for the Young's experiment. When the double slit is illuminated by monochromatic light (wavelength =5867 Å ), the centre of the screen appears dark rather than bright. The minimum thickness of the plastic sheet to be used for this to happen is
Options
- A3300 Å
- B6600 Å
- C2062 Å
- D5500 Å
Correct answer
D. 5500 Å
Step-by-step solution
Given, wavelength of monochromatic light, =5867 A Refractive index, =1.6 Let t be the thickness of the plastic. Since, the centre of the screen appears dark when plastic sheet is introduced, hence path difference, t= 2 or 3 2 when, t= 3 2 t= 3 2 = 3 5867 2 1.6 =5500