Answer:
668 bright fringes
Explanation:
t = Thickness = 0.2 mm
[tex]\lambda[/tex] = Wavelength = 600 nm
m = Number of fringes
We have the fringe width relation
[tex]2t=\left(m+\frac{1}{2}\right)\lambda\\\Rightarrow m=\dfrac{2t}{\lambda}-\dfrac{1}{2}\\\Rightarrow m=\dfrac{2\times 0.2\times 10^{-3}}{600\times 10^{-9}}-\dfrac{1}{2}\\\Rightarrow m=666.166\approx 667[/tex]
So, total number of fringes will be including m = 0 is [tex]1+667=668[/tex]