A photographic flash unit produces a brief burst of blue-green light centered at 480nm. The temporal variation of the flash’s optical output power P(t) may be approximated as follows:
• From t=0 to t=4.0ms the power increases linearly from 0 to a peak value of 24W.
• From t=4.0ms to t=8.0ms the power decreases linearly back to 0.
An imaging system collects 85% of the light emitted in this wavelength band and directs it onto a sensor array containing 5.0×106 pixels.
(a) Sketch the qualitative shape of P(t) over the 0 to 8.0ms interval, clearly indicating key values on both axes.
(b) Determine the total optical energy emitted by the flash during the entire 8.0ms interval.
(c) Calculate the total number of photons that actually reach the sensor array.
(d) Find the average number of photons incident on each pixel during a single flash exposure.
(e) Discuss how the photon statistics calculated in part (d) might influence image noise and exposure settings in low-light photography.