Light of wavelength 680 nm falls on two slits and produces an interference pattern in which the fourth-order fringe is 48 mm from the central fringe on a screen 1.5 m away. What is the separation of the two slits.

I am just confused with the manipulation of the formula dsin(theta)=m*wavelength.

Question

Light of wavelength 680 nm falls on two slits and produces an interference pattern in which the fourth-order fringe is 48 mm from the central fringe on a screen 1.5 m away. What is the separation of the two slits.  

I am just confused with the manipulation of the formula dsin(theta)=m*wavelength.

anonymous · Answer

you rather use the formula
$$a=\frac{ \lambda D }{ x }$$
a=separation of the two slits
D=Distance between the screen and the slits
x=fringe separation
$$\lambda = wavelength$$

anonymous · Answer

@sadon20

anonymous · Answer

Can you also solve it by finding the tangent angle in radians and then make it equal to m*lambda/d

anonymous · Answer

i do not know about that...