Answer to Question #43164 in Atomic and Nuclear Physics for Benjamin K

Question

A beam of C60 molecules (basically a molecule-sized ball that is 7.0 × 10^−10 m in diameter and has a mass of 1.2 × 10^−24 kg ) is directed at two small slits in a very thin metal sheet. The
molecules in the beam are travelling at 1 cm/s and the apparatus is in a vacuum. We would like to use this beam + slits to observe the wave properties of the molecules via diffraction.

a) What is the de Broglie wavelength of the molecules in the beam? (ANS: 5.5 x 10^-8 m)

b) Explain / calculate what size and spacing should be used for the slits in order to observe a
clear interference pattern on a screen 1 m away. (Hint: Depends on your assumptions.... but two slits, each 10 x 10^-6 m wide, spaced 55 x 10^-6 m apart would result in interference maxima 1 mm apart on the screen (which should be easily measurable).)