Question

Suppose the two glass plates in are two microscope slide l=12.0cm long. At one end they are in contact; at the other end, they are separated by a piece of paper h = 0.022 mm thick. What is the spacing of the interference finger's seen by reflection. Part A: Practice Problem: Suppose that we use two layers of paper, so that h = 4.40timesIU^5 m. What is the fringe spacing?

Answer 1

The thicknessof the fringe $\beta =\frac{L\lambda /2}{t}$

where L is length of the plate

t is thickness of the paper

the fringe width $\beta =\frac{0.12x250x10^{-9}}{0.022x10^{-3}}$

$\Rightarrow \beta =\frac{30}{0.022}x10^{-6}= 1.364x10^{-3}$ m

if thickness is increased, the denominator becomes twice, hence fringe width becomes half,

   $\Rightarrow \beta' =0.681x10^{-3}m$