Publicity often says that a new telescope can detect a candle across the Atlantic, etc. Well, a candlepower is defined as 1/683 Watts at 540 X 10^9Hz. This gives photon energy at 2.2 eV. One candlepower produces 4.2 x 10^15 photons/s radiated isotropically. At 3,000km the area of the sphere is about 10^14m^2 So the photon density at the telescope is 4.2 x 10^15/10^14 or about 4 photons per sq meter per second. Two things to note: The associated electromagnetic field would be very small, but not zero. A second is a long time in quantum matters. My questions are: How do you demonstrate the area covered by a photon at the telescope mirror ? How long is the photon wavetrain ? (I can’t believe I’m asking this) does the field collapse to the photon particle ? Is this like the photoelectric effect where a classical calc shows that 10 minutes or so would be required to dislodge the electron, where in fact it occurs in about 10^-9s.