Question

The human eye is able to detect as little as 2.35 x10 Jof green light of wavelength 510 nm. Calculate the minimum number of photons of green light that can be detected by the human eye. Physical constants can here. Number number of photons- photons

Answer 1

From the given data

Wavelength = 510 nm

then

Energy E = h.f

where h = Plancks constant , f is frequency

Now

f x $\lambda$ = c then f = c / $\lambda$

therefore

E = h.c / $\lambda$

then for one photon , Energy will be

E = 6.626 x 10^-34 m².J/s x 3 x 10⁸ m/s / 510 x 10^-9 m

= 3.89 x 10^-19 J

We have amount of energy 2.35 x 10^-18 J

then for number of photons

Number of Photons = 2.35 x 10^-18 J / 3.89 x 10^-19 J

= 6.03