Question

Chapter 24: Antireflective Coating What is the minimum thickness of m Express your answer in nanometers. tabulte (known as the substrate). The index of View Available Hints) Figure Air rays Polystyrene1.49 n2409 Fabulite Constants Express your answer in meters has a d/15. The lasers prockuce 20, Interference patterns on a screen View Available Hint(s) e 5.60 m 0.0767m Previous Answers Part C What is the distance Express your answer in meters. View Available Hin (s)

Answer 1

Non reflecting coating:

                                  This implements the principal of interference, here there are no energy loss due reflection. The energy lost in reflection appears in transmission. Hence surface of glass is coated with non reflecting coating.

The thickness of non reflecting film is
t= 1+
   here $\lambda$ is wavelength of light and $\mu$ is refractive index

450 4*149 10-9 7n

thickness of film is t=75.5nm.

Double slit.

Fringe width is

* 2

D is distance between screen and double slits and 2d is distance between two slits.

for Laser source 1.

5.6m 20

so

3 = 0.28m

for laser source 2.

d * 5.6m 15

so

0.17m

Hence distance between first maximas (n=1) is = (0.28-0.17)m=0.11m