In this paper we report on the use of two different light to frequency
converters, four different light sources, three of which are novel and
inexpensive, and a hand held digital multimeter with a frequency counter,
suitable for making accurate and rapid determination of the optical inverse
square law exponent of −2 to better than ±0.005 over more than a factor of
100 in distance and a factor of 5 × 105 variation of light intensity. Accurate
data sets can be taken in 20–40 min, typically one minute per data point or
less.