*9.  mmh In a Young’s double-slit experiment the separation y between the second-order bright fringe and the central bright fringe on a flat screen is 0.0180 m when the light has a wavelength of 425 nm. Assume that the angles that locate the fringes on the screen are small enough so that sin q » tan q. Find the separation y when the light has a wavelength of 585 nm.

Bright Fringes in a double-slit experiment have the defining equation

 

 

Tangent of the angle can be found by

 

Using the approximation suggested

 

So our bright condition becomes

 

Solve for separation y

 

So for the first wavelength we have

 

And for the second

 

Since the combination  never changes, we can solve for y2 by dividing the equations

 

Solve for y2

 

 

 

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This page last updated on July 7, 2018