Question

Two flat glass plates are separated at one end by a wire of diameter 0.20 mm; at the other end they touch. Thus, the air gap between the plates has a thickness ranging from 0 to 0.20 mm. The plates are 15.0 cm long and are illuminated from above with light of wavelength 600.0 nm. How many bright fringes are seen in the reflected light?

Answer 1

668 bright fringes

Step-by-step explanation:

t = Thickness = 0.2 mm

`\lambda` = Wavelength = 600 nm

m = Number of fringes

We have the fringe width relation

`2t=\left(m+(1)/(2)\right)\lambda\\\Rightarrow m=(2t)/(\lambda)-(1)/(2)\\\Rightarrow m=(2* 0.2* 10^(-3))/(600* 10^(-9))-(1)/(2)\\\Rightarrow m=666.166\approx 667`

So, total number of fringes will be including m = 0 is
`1+667=668`