Problem 14-10 Double Slit - B

A laser beam with light of wavelength \(638.2\; nm\) is used to check a manufacturer's claim that a double slit has a separation of \(0.200\; mm.\) The distance to the screen is \(3.00\; m\) and the measured distance from the central maximum to the middle of the fourth minimum is \(33.2 \;mm.\) What is the measured slit separation?
[Ans. \(0.202 \;mm\)]

Accumulated Solution
Diagram of laser beam.


The relation for a minimum in double slit interference is:

(A)   \(x/L = M\lambda/d\)

(B)   \(x/L = (N-1) \lambda/d\)

(C)   \(x/L = (N-½)\lambda/d\)