The following items are positioned in sequence: A source of a beam of natural light of intensity I₀,three ideal polarizers A,B,and C;and an observer.Polarizer axis angles are measured clockwise from the vertical,as viewed by the observer.The axis angle of polarizer A is set at 0° (vertical),and the axis angle of polarizer C is set at 50°.Polarizer B is set so that the beam intensity at the observer is a maximum.What is the axis angle settings of polarizer B? A)0° B)25° C)50° D)75° E)100°

Question

Quizplus · Accepted Answer

Since the intensity of natural light is given as I₀, we can assume that the initial intensity of the beam is 1. The polarizer axis angle of A is 0°, which means it vertically polarizes the beam. The polarizer axis angle of C is 50°, which means it transmits 50% of the vertically polarized light and 50% of horizontally polarized light. Let the polarizer axis angle of B be x. Then, the intensity of the beam transmitted by polarizer A is cos²(0°) = 1. The intensity of the beam transmitted by polarizer C is 0.5 cos²(50°) + 0.5 sin²(50°) = 0.5. Since the beam intensity at the observer is a maximum when passing through polarizer B, polarizer B must transmit all of the vertically polarized light from polarizer A and all of the horizontally polarized light from polarizer C. Thus, the angle of polarizer B should be halfway between the angles of polarizers A and C, which is 25°. Therefore, the answer is B.

The Following Items Are Positioned in Sequence: a Source of a Beam