Solution to task 515 from Chertov´s for extramural stud

Solution to task 515 from Chertov´s for extramural stud

515. A parallel X-ray beam falls on the face of the rock salt crystal. The distance d between the atomic planes is 280 pm. A first-order diffraction maximum is observed at an angle ϑ = 65 ° to the atomic plane. Determine the wavelength λ of X-ray radiation.