In a typical picture, the average number of photons that hit each pixel is approximately 4.
The camera's detectors will see (D.) random pixels will have exactly one excited electron, while others will have no excited electrons.
How to find photons?
Part 1: Average Number of Photons per Pixel
Convert watts to joules:
Energy = Power × Time
Energy = 4.5 × 10⁻⁶ watts × 10 × 10⁻³ seconds
Energy = 4.5 × 10⁻⁸ joules
Calculate the energy of one photon:
Energy per photon = (hc) / λ
where:
h = Planck's constant = 6.626 × 10⁻³⁴ J s
c = speed of light = 3 × 10⁸ m/s
λ = wavelength of light = 535 × 10⁻⁹9 m
Energy per photon = (6.626 × 10⁻³⁴ J s) × (3 × 10⁸ m/s) / (535 × 10⁻⁹ m)
Energy per photon = 3.704 × 10⁻¹⁹ J
Calculate the number of photons:
Number of photons = Total energy / Energy per photon
Number of photons = 4.5 × 10⁻⁸ joules / 3.704 × 10⁻¹⁹ J/photon
Number of photons ≈ 1215
Calculate the average number of photons per pixel:
Total pixels = 2000 × 1500
= 3 × 10⁶
Average photons per pixel = 1215 photons / 3 × 10⁶ pixels
Average photons per pixel ≈ 4 photons
Therefore, in a typical picture, the average number of photons that hit each pixel is approximately 4.
Part 2: Detectors with Low Intensity Light
With very low intensity green light (4 × 10⁻¹¹ watts) illuminating the detector array, the number of photons hitting each pixel will be significantly lower than in the previous scenario.
Random pixels with one excited electron: This is the most likely scenario. With very low light intensity, the probability of a single photon hitting each pixel during the exposure time is much higher than multiple photons hitting the same pixel. Therefore, it's expected to see a random pattern of pixels with either one excited electron or none.
Therefore, the most likely observation for the camera's detectors under low intensity light is D - Random pixels will have exactly one excited electron, while others will have no excited electrons.