Answer:
1
When second polarizer is removed the intensity after it passes through the stack is

2 When third polarizer is removed the intensity after it passes through the stack is

Explanation:
From the question we are told that
The angle of the second polarizing to the first is
The angle of the third polarizing to the first is 
The unpolarized light after it pass through the polarizing stack 
Let the initial intensity of the beam of light before polarization be 
Generally when the unpolarized light passes through the first polarizing filter the intensity of light that emerges is mathematically evaluated as

Now according to Malus’ law the intensity of light that would emerge from the second polarizing filter is mathematically represented as


The intensity of light that will emerge from the third filter is mathematically represented as

![I_3= \frac{I_p}{2}(cos^2 \theta_1)[cos^2(\theta_2 - \theta_1)]](https://tex.z-dn.net/?f=I_3%3D%20%5Cfrac%7BI_p%7D%7B2%7D%28cos%5E2%20%5Ctheta_1%29%5Bcos%5E2%28%5Ctheta_2%20-%20%5Ctheta_1%29%5D)
making
the subject of the formula
![I_p = \frac{2L_3}{(cos^2 \theta [cos^2 (\theta_2 - \theta_1)])}](https://tex.z-dn.net/?f=I_p%20%3D%20%5Cfrac%7B2L_3%7D%7B%28cos%5E2%20%5Ctheta%20%5Bcos%5E2%20%28%5Ctheta_2%20-%20%5Ctheta_1%29%5D%29%7D)
Note that
as
is the last emerging intensity of light after it has pass through the polarizing stack
Substituting values
![I_p = \frac{2 * 60 }{(cos^2(21) [cos^2 (61-21)])}](https://tex.z-dn.net/?f=I_p%20%3D%20%5Cfrac%7B2%20%2A%2060%20%7D%7B%28cos%5E2%2821%29%20%5Bcos%5E2%20%2861-21%29%5D%29%7D)
![I_p = \frac{2 * 60 }{(cos^2(21) [cos^2 (40)])}](https://tex.z-dn.net/?f=I_p%20%3D%20%5Cfrac%7B2%20%2A%2060%20%7D%7B%28cos%5E2%2821%29%20%5Bcos%5E2%20%2840%29%5D%29%7D)

When the second is removed the third polarizer becomes the second and final polarizer so the intensity of light would be mathematically evaluated as

is the intensity of the light emerging from the stack
substituting values


When the third polarizer is removed the second polarizer becomes the
the final polarizer and the intensity of light emerging from the stack would be

is the intensity of the light emerging from the stack
Substituting values

