Question

Thin film examples Suppose the two glass plates in the figure are two microscope slides 10 cm long. They are in contact at one end and are separated by a piece of paper 0.020 mm thick at the other end. What is the spacing of the interference fringes seen by reflection? Is the fringe at the line of contact bright or dark? Assume monochromatic light with λ-500 nm. λο 500 nm h - 0.020 mm 1 10.0 cm

Answer 1

answer) we know the formula dark fringes

2t=m $\lambda$ ...........1)

now we have to use the property of similar triangle

t/x=h/l

t=xh/l

replacing the value of t in 1)

2xh/l=m $\lambda$

x=m $\lambda$ l/2h,

now plugging all the known values we have

x=m*500*10^-9*0.1/2*0.02*10^-3=1250*10^-3 m=1.25 mm

so the answer is 1.25 mm