Light from a laser is directed normally at a diffracted grating, as illustrated in the figure below.
The diffraction grating is situated at the center of a circular scale, marked in degrees. The readings on the scale for the second order diffracted beams are and .
The wavelength of the laser light is .
Calculate the spacing of the slits of the diffraction grating.
because there are I took 2 reading? or is there another reason?