Question

Suppose 10-J of light energy is needed by the interior of the human eye to see on object. How many photos of
light ( = 550 nm) are needed to generate this minimum amount of energy?​

Answer 1

✔

E = hc/(wavelength)

so, for wavelength = 550nm 

then energy of 1 photon is

E =6.626 x 10-34 J·s x 3 x 108 m/sec/ (550nm x 10-9 m)

E = 3.61 × 10^-19 J

now 

✅nE = 10^-17

so, n = 10^-17/(3.61 × 10^-19) = 100/3.61 = 27.7 = 28.