2-11 Slit widtıh in an atomic beam apparatus. (a) The diffraction of plane waves of wavelength A by a slit of width d is characterized by an angular spread of the order of /d. At a distance D beyond the slit, this makes the beam broader than d by a distance of the order of DA/d. If a and D are given, what condition on d makes this spreading relatively unimportant? (b) In an atomic beam apparatus, potassium metal (atomic weight 39) is heated to its boiling point (7 = 760°C = 1000 K) and streams out of the oven aperture as individual atoms (at average energy = kT 1/10eV, where k is Boltzmann's constant = 1.38 × 10-1 erg/degree Kelvin and 7 is in degrees Kelvin) in- to a vacuum chamber. The experimenter wishes to make the beam narrower and masks it down with a slit 0.1 mm wide. The detector is located 50 cm downstream from the slit. By what percentage (approx- imately) is the beam made broader than the geometrical image of the slit as a result of diffraction?

2-11 Slit widtıh in an atomic beam apparatus. (a) The diffraction of plane waves of wavelength A by a slit of width d is characterized by an angular spread of the order of /d. At a distance D beyond the slit, this makes the beam broader than d by a distance of the order of DA/d. If a and D are given, what condition on d makes this spreading relatively unimportant? (b) In an atomic beam apparatus, potassium metal (atomic weight 39) is heated to its boiling point (7 = 760°C = 1000 K) and streams out of the oven aperture as individual atoms (at average energy = kT 1/10eV, where k is Boltzmann's constant = 1.38 × 10-1 erg/degree Kelvin and 7 is in degrees Kelvin) in- to a vacuum chamber. The experimenter wishes to make the beam narrower and masks it down with a slit 0.1 mm wide. The detector is located 50 cm downstream from the slit. By what percentage (approx- imately) is the beam made broader than the geometrical image of the slit as a result of diffraction?