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Minimum light intensity that can be perc...

Minimum light intensity that can be perceived by normal human eye is about `10^-10 W m^-2`. What is the minimum number of photons of wavelength 660 nm that must enter the pupil in one second, for one to see the object ? Area of cross-section of the pupil is `10^-4 m^2` ?

A

`33 xx 10^2`

B

`33 xx 10^3`

C

`33 xx 10^4`

D

`33 xx 10^5`.

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