The minimum light intensity that can be perceived by the eye is about $10^{10}\ Wm^{- 2}.$ The number of photons of wavelength $5.6 imes 10^{- 7}$m that must enter the pupil of area $10^{- 4}m^{3}s^{- 1}$, for vision is approximately equal to $(h = 6.6 imes 10^{- 34}$J-s)

Question

The minimum light intensity that can be perceived by the eye is about $10^{10}\ Wm^{- 2}.$ The number of photons of wavelength $5.6 	imes 10^{- 7}$m that must enter the pupil of area $10^{- 4}m^{3}s^{- 1}$, for vision is approximately equal to $(h = 6.6 	imes 10^{- 34}$J-s)

Dr. Abubacker · Accepted Answer

(c) Light intensity $= 10^{- 10}W\ m^{- 2}.$ So energy falling on area of point to be perceived
$= 10^{- 10} 	imes 10^{- 4} = nhc/\lambda$
or $n = \frac{10^{- 14} 	imes 5.6 	imes 10^{- 7}}{6.6 	imes 10^{- 34} 	imes 3 	imes 10^{8}} = 3 	imes 10^{4}$

Q. The minimum light intensity that can be perceived by the eye is about $10^{10}\ Wm^{- 2}.$ The number of photons of wavelength $5.6 \times 10^{- 7}$m that must enter the pupil of area $10^{- 4}m^{3}s^{- 1}$, for vision is approximately equal to $(h = 6.6 \times 10^{- 34}$J-s)

Explanation

Reviewed by Dr. Abubacker

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