The human eye can detect light intensities as small as about 2 10-23 W/m2. (a) W
ID: 1509237 • Letter: T
Question
The human eye can detect light intensities as small as about 2 10-23 W/m2. (a) What is the corresponding electric field amplitude? Incorrect: Your answer is incorrect. N/C (b) Suppose the eye senses this light by detecting the force on electrons inside a photoreceptor cell within the eye. What is the electric force exerted on an electron by the electric field found in part (a)? Incorrect: Your answer is incorrect. N (c) How does this force compare to the weight of an electron? electric force weight of electron = Incorrect: Your answer is incorrect.
Explanation / Answer
let,
intensity, I=2*10^-23 W/m^2
a)
intensity, I=1/2*eo*c*E^2
2*10^-23=1/2*(8.85*10^-12*3*10^8*E^2)
electric field, E=1.23*10^-10 N/c
b)
force, F=q*E
F=(1.6*10^-19)*1.23*10^-10
F=1.968*10^-29
c)
weight of the electron,
W=m*g
W=9.1*10^-31*9.8
w=8.92*10^-30 N
and
F/W=1.968*10^-29/(8.92*10^-30)
==>
F=2.21*W
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