Unpolarized light with an intensity of 655 W / m2 is incident on a polarizer with an unknown axis. The light then passes through a second polarizer with has an axis which makes an angle of 81.5° with the vertical. After the light passes through the second polarizer, its intensity has dropped to 163 W / m2. What angle does the first polarizer make with the vertical?

Respuesta :

Answer:

1.[tex]\theta=29.84^{0}[/tex]

2.[tex]\theta=60.15^{0}[/tex]

Explanation:

Polarizes axis can create two possible angles with the vertical.

first we have to find the intensity of  first polarizer

which is given as

[tex]I=\frac{I_{0} }{2}[/tex]

[tex]I= \frac{655\frac{W}{M^{2} } }{2}[/tex]

[tex]I=327.5\frac{W}{m^{2} }[/tex]

For a smaller angle for the first polarizer:

According to Malus Law

[tex]I_{2} =I_{1} Cos^{2}(90^{0} - \theta)[/tex]

[tex]I_{2} =I_{1} sin^{2}\theta[/tex]

[tex]\frac{I_{2} }{I_{1} }=Sin^{2}\theta[/tex]

taking square root on both sides

[tex]\sqrt{\frac{163}{327.5} } = sin\theta[/tex]

[tex]\theta=Sin^{-1}(0.4977)[/tex]

[tex]\theta=29.84^{0}[/tex]

For a larger angle for the first polarizer:

According to Malus Law

[tex]I_{2} =I_{1} cos^{2}\theta[/tex]

[tex]\frac{I_{2} }{I_{1} }=Cos^{2}\theta[/tex]

taking square root on both sides

[tex]\sqrt{\frac{163}{327.5} } = cos\theta[/tex]

[tex]\theta=Cos^{-1}(0.4977)[/tex]

[tex]\theta=60.15^{0}[/tex]