Question

15. Unpolarized light is sent through three linear polarizers. The transmission axis (TA) of each new polaris indicated. If the incident light has an intensity of 25.0 W/m , what is the final intensity of the light the passing through all three polarizes! = 45.0 and 8 - 30.0"

Answer 1

14) The ocean waves interfere after passing through double slits. The angle between the line passing through the final position of the boat and the horizontal line drawn is given by

$\theta=\tan^{-1}(60/100)=\tan^{-1}(0.6)=30.96^o$

The condition for the first minima is

$d\sin\theta=\frac{\lambda}{2}$

where d is the separation between the 2 slits which is 40 m

Therefore the wavelength of the ocean wave is

$\lambda=2d\sin\theta=2\times 40\times \sin(30.96^o)=41.16\,m$

15) After passing through the first polarizer the intensity reduces by half.

The angle between the second and the first polarizer is 45 degrees. Hence the intensity reduces by a factor of

$\cos^2 45^o$

after passing through the second polariser.

The angle between the second and the third polarizer is 90 - 30 = 60 degrees. Hence the intensity reduces by a factor of

$\cos^2 60^o$

after passing through the third polariser.

The net final intensity is

$I=\frac{I_o}{2}\cos^245^o\cos^2 60^o=\frac{25}{2}\times 0.5\times 0.25=1.56\,\,W/m^2$