Due to the quantum mechanical wave nature of particles, diffraction effects have also been observed with atoms—effects which are similar to those in the case of light. Chapman et al. carried out an experiment in which a collimated beam of sodium atoms was passed through two diffraction gratings (the second used as a mask) to observe the Talbot effect and measure the Talbot length.[5] The beam had a mean velocity of 1000 m/s corresponding to a de Broglie wavelength of λ dB {\displaystyle \lambda _{\text{dB}}} = 0.017 nm.