Explanation:
Given that,
The wavelength of light = 580 nm
Slit separation, d = 0.000125 m
We need to find the angle of the third dark interference. For the dark fringe,
[tex]d\sin\theta=(m+\dfrac{1}{2})\lambda[/tex]
Put m = 3 and other values also.
[tex]d\sin\theta=(3+\dfrac{1}{2})\lambda\\\\d\sin\theta=\dfrac{7\lambda}{2}\\\\\sin\theta=\dfrac{7\lambda}{2d}\\\\\theta=\sin^{-1}(\dfrac{7\lambda}{2d})\\\\\theta=\sin^{-1}(\dfrac{7\times 580\times 10^{-9}}{2\times 0.000125 })\\\\\theta=0.93^\circ}[/tex]
So, the angle is 0.93°.
