Solving a problem in physics section 18 point 41 optics

Solving a problem in physics section 18 point 41 optics

41. At the grating normally incident monochromatic light with a wavelength λ = 0,5mkm. The display, located at a distance from the lattice L = 1 m, with a lens located near the grating, the diffraction pattern is projected, with the first main peak is observed at a distance l = 15 cm from the center. Determine the number of lines per 1 cm grating.

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Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)