You find an unmarked blue laser on your way to physics class

You find an unmarked blue laser on your way to physics class. When you get to class you realize you can determine the wavelength of the laser by doing a double slit experiment. Shining the laser through a double slit with a slit separation of 0.335 mm on the wall 2.18 m away the first bright fringe is 2.92 mm from the center of the pattern. What is the wavelength? in nm

Solution

the wavelength is calculated as follows:

    lambda = yd/mD

                =2.92X10^-3* 0.335X10^-3 / 1*2.18

                = 4.487e-7 m

                = 448.7 nm