Question

The human eye is a complex sensing device. The optic nerve needs a minimum of 2.10x10^-17J of energy to trigger a series of impulses that eventually reach the brain. How many photons of blue light (475nm) are needed? The human eye is a complex sensing device. The optic nerve needs a minimum of 2.10x10^-17J of energy to trigger a series of impulses that eventually reach the brain. How many photons of blue light (475nm) are needed? @Chemistry

Answer 1

use planks relation which gives you the energy in terms of ONE photon:

E=hv

E= energy in joules (J)
h= planks constant
v= frequency, which equals the speed of light/lwavelength = c/lambda

in this relation the wavelength is expressed in meters, so you have to convert nm to meters.

E=hc/lambda

so find the energy one photon of this wavelength produces then find out how many photons you need by dividing the energy you need by the amount of energy of one photon