Can someone help and show me how to actually do this problem? Three polarizers a
ID: 1515189 • Letter: C
Question
Can someone help and show me how to actually do this problem? Three polarizers are stacked one on top of each other. The first polarizer has its transmission axis alon the x axis, the third has its transmission axis along the y axis. (the x and y axis are 90 degrees apart) The second polarizer is in between the first and third polarizer. You are free to rotate the second polarizer so that its transmission angle is in any direction. Unpolarized light with an intensity of 1000 W/m^2 passes through all three polarizers.
1. If the second polariser is oriented at 30 degrees from the first polarizer, what is the magnitude of intensity of light that leaves all three polarizers?
A. 0 W/m^2 B. 75 W/m^2 C. 94 W/m^2 D. 145 W/m^2 E. 225 W/m^2
2. If frequency of light emitted from a distant star is fs = 4.50x10^4 Hz. and the frequency of light that we observe coming from that start is fo = 4.22x10^1 Hz. What is the speed of the star with respect to earth?
A. 1.33 x10^7 m/s B. 1.87 x 10 ^7 m/s C. 2.43 x 10^7 m/s
Explanation / Answer
1) C) 94 W/m^2
Let Io = 1000 W/m^2
Intensity through first polarizer, I1 = Io/2
= 1000/2
= 500 W/m^2
Intensity through second polarizer,
I2 = I1*cos^2(30)
= 500*cos^2(30)
= 375 W/m^2
Intensity through third polarizer,
I3 = I2*cos^2(90-60)
= 375*cos^2(60)
= 93.75 W/m^2
2)
fo = fs*c/(c+v)
c + v = fo*c/fs
v = fo*c/fs - c
= c*(fo/fs - 1)
= 3*10^8*(4.5*10^4/(4.22*10^4) - 1)
= 2*10^7 m/s