In Figure ( a ) below, unpolarized light is sent into a system of three polarizi
ID: 1453999 • Letter: I
Question
In Figure (a) below, unpolarized light is sent into a system of three polarizing sheets. The angles ?1, ?2, and ?3 of the polarizing directions are measured counterclockwise from the positive direction of the y axis (they are not drawn to scale). Angles ?1 and ?3 are fixed, but angle ?2 can be varied. Figure (b) gives the intensity of the light emerging from sheet 3 as a function of ?2. (The scale of the intensity axis is not indicated.) What percentage of the light's initial intensity is transmitted by the system when ?2 = 51o?
0 0° 90° 180 2Explanation / Answer
2 = 90 --------------> 3= 90 + 90 = 180
2 = 180 ------------> 1=180 - 90 = 90
When it passes through the first polarizing sheet, the light is initially unpolarized(its intensity is I0), so the intensity drops by half.
After passing through the second polarizer it is further reduced by a factor of cos2(-1-2) = cos2(1+2)
After passing throught the third one the intensity is again reduced by a factor of cos2(-2-3) = cos2(2+3)
Ratio of final intensity to initial intensity,
If/I0 = (1/2)cos2(1+2)cos2(2+3)
= (1/2)cos2(90o+51o)cos2(51o+180o)
=0.1196
Therefore 11.96% of the lights initial intensity is transmitted.