1. 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
```

2. 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
```

3. 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)
```

4. 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
```

5. 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
```