X-rays of wavelength 0.133 nm fall on a crystal whose atoms, lying in planes, are spaced 0.280 nm apart. At what angle (relative to the

X-rays of wavelength 0.133 nm fall on a crystal whose atoms, lying in planes, are spaced 0.280 nm apart. At what angle Φ (relative to the surface, Fig.25-37) must the X-rays be directed if the first diffraction maximum is to be observed?