Answer:2 ft/s
Explanation:
Given
Length of Pole is 9 ft
Length of Joe is 3 ft
Joe walks away from Pole at the rate 4 ft/s
Let Joe is x m away from Pole so its shadow length is x'
From Similar triangle concept

3x'=x+x'
x=2x'
and it is given 
Differentiating



To solve this problem it is necessary to apply the concepts related to Malus' law. Malus' law indicates that the intensity of a linearly polarized ray of light that passes through a perfect analyzer with a vertical optical axis is equivalent to:

Indicates the intensity of the light before passing through the Polarizer,
I = The resulting intensity, and
= Indicates the angle between the axis of the analyzer and the polarization axis of the incident light.
There is 3 polarizer, then
For the exit of the first polarizer we have that the intensity is,

For the third polarizer then we have,

Replacing with the first equation,



Therefore the transmitted intensity now is
of the initial intensity.
Well first you can not go to the 2nd energy level without the first so the first takes up 2 electrons leaving you 5 electrons and the recommended amount is 8 electrons so you would have 5 electrons left