Answers to questions about Taylor's experiment

What was the flux of energy per square cm per second in Taylor's experiment?

         The paper states that this flux is

             F  =  5 x 10^(-6)  ergs per square cm per sec

                   5 x 10^(-13) Joules per square cm per sec

Assume the light was yellowish, with wavelength lambda = 550 nm. What is the energy of each photon, in ergs? How many photons strike one square cm each second?

         The energy of a photon is

            E   =    h * nu   =   (h * c) / lambda

                =    3.6 x 10^(-19)  Joules

                =    3.6 x 10^(-12)  ergs


         so the number of photons striking one square cm 
         each second must be

           N    =   F  /  E   =  1.38 x 10^6  photons per square cm per sec

Photographic film responds to light because it contains grains of silver halide. Each grain is roughly 2 micrometers in diameter. How many grains are there in one square cm?

         If the grains are assumed to be packed in a simple
         square grid, then 

            N(top)  =  number of grains across top of 1 square cm

                    =   (1 cm) / (2 x 10^(-6) m)  =  5000

            N(left) =  number of grains across left side of 1 square cm

                    =   (1 cm) / (2 x 10^(-6) m)  =  5000

          N(grains) =  (number across top) * (number along left edge)

                    =   5000 * 5000  =  25 x 10^(6)

How many photons strike a grain each second?


         If the N photons hitting each square cm in one second
         are randomly distributed across the entire square,
         then the number landing on any particular grain
         in one second must be

              N / N(grains)   =   1.38 x 10^6  /  25 x 10^6

                              =   0.055  photons per grain per second

What is the interval between successive photons striking a grain in Taylor's experiment?

         The average interval between successive photons
         hitting the same grain is just the reciprocal of the
         number of photons hitting the grain each second.


               interval      =   1  /  (0.055 photons per grain per second)

                             =   18 seconds between photons