The training of physics teachers in remote areas in the developing world requires dedicated trainers
(who typically are volunteers), as well as robust logistics. The latter must include the supply of
equipment for experiments in the classroom. This task is greatly aided by the use of cheap, safe and
readily available consumer goods that do not require local power supplies. In this paper, a simple
experiment using a laser pointer pen and samples of hair as well as wire and transparent thin fibre
is presented, reproducing a variant of Thomas Youngs’ famed double slit experiment. The spread of
the interference pattern as it projects itself on a screen is sufficiently large to catch the
interest of students, and its orientation being perpendicular to that of the hair is also strikingly
counter-intuitive. The students are then encouraged to apply the simplified Fraunhofer equation to
the various samples to find out the width of their hair. Ideally, these samples would also include
ca…