|
Title: The human eye is a complex sensing device for visible light.? Post by: oapplesauce on Sep 16, 2012 The optic nerve needs a minimum of 2.0 x 10^-17 J of energy to trigger a series of impulses that eventually reach the brain. How many photons of blue light (475nm) are needed?
Title: The human eye is a complex sensing device for visible light.? Post by: oby on Sep 16, 2012 the energy of a photon is hv, where v is the frequency, and h is Planck's constant, about 6.63E-34
you don't have the frequency but you have the wavelength, lambda = 4.75E-7 and there is the relationship c = lambda * nu (wavelength times frequency) so nu = c/lambda = 3E8 / 4.75E-7 = 6.32E14 so the energy of your blue photon is: E = hv = 6.63E-34 * 6.32E14 = 4.18E-19 J So to get to 2E-17 J, you'll need 47.8 photons but you can't get a bit of a photon, so that'll be 48 photons please Incidentally, this is massively better than most currently available imaging devices out there. and, the retina has about 125 megapixels, on an area the size of "APS" sensors in DSLR's, which have about 12megapixels these days (really high-end cameras have more, but their sensors are also bigger) so it looks like it'll be at least another 8-10 years until image sensors maybe match what our eyes can do... ;-) |