Unpolarized light with intensity 370 W/m2 passes first through a polarizing filter with its axis vertical, then through a second polarizing filter. It emerges from the second filter with intensity 138 W/m2 .
a. What is the angle from vertical of the axis of the second polarizing filter?b. Express your answer to two significant figures and include the appropriate units

Respuesta :

To solve this problem it is necessary to apply the concepts given by Malus regarding the Intensity of light.

From the law of Malus intensity can be defined as

[tex]I' = \frac{I_0}{2} cos^2 \theta[/tex]

Where

[tex]\theta =[/tex]Angle From vertical of the axis of the polarizing filter

[tex]I_0 =[/tex] Intensity of the unpolarized light

The expression for the intensity of the light after passing through the first filter is given by

[tex]I = \frac{I_0}{2}[/tex]

Replacing we have that

[tex]I = \frac{370}{2}[/tex]

[tex]I = 185W/m^2[/tex]

Re-arrange the equation,

[tex]I'= \frac{I_0}{2}cos^2\theta[/tex]

Re-arrange to find \theta

[tex]cos^2\theta = \frac{2I'}{I_0}[/tex]

[tex]cos^2\theta = \frac{2*138}{370}[/tex]

[tex]\theta = cos^{-1}(\sqrt{\frac{2*138}{370}})[/tex]

[tex]\theta = 0.5282rad[/tex]

[tex]\theta = 30.27\°[/tex]

The value of the angle from vertical of the axis of the second polarizing filter is equal to 30.2°

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