Wavelength of electrons (\\lambda) = \\dfrac{12.27}{\\sqrt{V}} \\mathring A = \\dfrac{1227}{\\sqrt{54}} \\mathring A = \\dfrac{12.27}{7.348} \\mathring A = 1.669 \\mathring A \\approx 1.67 \\mathring A Perpendicular distance in diffraction pattern = d \\, sin \ heta Perpendicular distance for first order = \\dfrac{\\lambda}{2} \ herefore sin \ heta = \\dfrac{\\lambda}{2d} = \\dfrac{1.67 \\mathring A}{2 \ imes 0.92 \\mathring A} = 0.907 \ heta = 65^{\\circ}