Optics Question 566
Question: Unpolarized light of intensity 32Wm?2 passes through three polarizers such that transmission axes of the first and second polarizer makes and angle 30° with each other and the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light will be
Options:
A) 32 Wm?2
B) 3 Wm?2
C) 8 Wm?2
D) 4 Wm?2
Show Answer
Answer:
Correct Answer: B
Solution:
Angle between P1 and P2 = 30° (given) Angle between P2 and P3 = q = 90° - 30° = 60°
The intensity of light transmitted by P1 is $ I _{1}=\frac{I _{0}}{2}=\frac{32}{2}=16\frac{W}{m^{2}} $ .
According to Malus law the intensity of light transmitted by P2 is $ I _{2}=I _{1}{{\cos }^{2}}30{}^\circ =16{{( \frac{\sqrt{3}}{2} )}^{2}}=12\frac{W}{m^{2}} $ .
Similarly intensity of light transmitted by P3 is $ I _{3}=I _{2}{{\cos }^{2}}\theta =12{{\cos }^{2}}60{}^\circ =12{{( \frac{1}{2} )}^{2}}=3\frac{W}{m^{2}} $
