An owl has good night vision because its eyes can detect a light intensity as small as 5.0 × 10-13 w/m2. what is the minimum number of photons per second that an owl eye can detect if its pupil has a diameter of 8.5 mm and the light has a wavelength of 548 nm?

Thus, the minimum number of photons per second is 77.34

Explanation:

Light intensity, =  

Pupil has a diameter, d = 8.5 mm

                                      = 8.5 x m

Radius of the eye, r = 4.25 x m

∴ Area of the eye, A =

                                 =

                                =

Let be the minimum number of photons.

Therefore, = x A

                                              = x

                                             = W

Thus the minimum number of photons is given by

where E =

             =

            =

Therefore, =

                                              = 77.34 photons per second

Thus, the minimum number of photons per second is 77.34