Question

The eyes of reptile pass a single visual signal to the brain when the visual receptors are struck by photons of wavelength of 850 nm. If a total energy of 3.15 x 10-14 J is required to trip the signal, what is the minimum number of photons that must strike the receptor?

Answer 1

Answer: The minimum number of photons that must strike the receptor is
`135* 10^3`

Step-by-step explanation:

The relation between energy and wavelength of light is given by Planck's equation, which is:

`E=(Nhc)/(\lambda)`

where,

E = energy of the light =
`3.15* 10^(-14)J`

N= Number of photons = ?

h = Planck's constant =
`6.6* 10^(-34)`

c = speed of light =
`3* 10^8m/s`

`\lambda` = wavelength of light =
`850nm=850* 10^(-9)m (1nm=10^(-9)m)`

`3.15* 10^(-14)=(N* 6.6* 10^(-34)* 3* 10^8)/(850* 10^(-9)m)`

`N=135* 10^3`

Thus the minimum number of photons that must strike the receptor is
`135* 10^3`