The eyes of a reptille pass a visual signal what is minimum number of photons that must strike the receptor `(h = 6.6 xx 10^(-34))`?

Explanation

`E = (hc)/(lambda) = (6.6 xx 10^(-34) xx 3 xx 10^(8))/(850 xx 10^(-9)) = 2.3 xx 10^(-19) J`
Energy required to trip signal `= 3.15 xx 10^(-14) J`
`m xx E = E_(total)` photons that strike the recptor are
`n = (3.15 xx 10^(-16))/(2.5 xx 10^(-19)) = 1.37 xx 10^(5)` photrons