Problem 18: A car is traveling North on a straight road, towards two radio transmission towers, S1 and S2. Transmitter S1 is located very close to the road; S2 is located at some distance d to the East of S1. (Draw this!) The two transmitters are oscillating in phase at a frequency of 91.7 MHz, sending out radio wave crests and troughs in synchrony. The car radio is tuned to the 91.7 MHz radio station and receives a strong radio signal when the car is still several km away from Sı and S2. However, as the car approaches the transmitters, the radio signal gets weaker, and the radio signal disappears altogeter, due to destructive interference, when the car reaches a distance of 690 m from S1. What is the distance, d, between the two radio transmitters? Hints: Consider the pathlength difference, Al := l2 – l1, where l2 is the distance from S2 to the car and and l1 is the distance from S1 to the car. (1) Initially, when the car is very, very far away from S1, i.e., in the limit l1 → ∞, the pathlength difference vanishes: Al → 0. (2) As the car approaches S1, the value of Al increases as l, decreases. (3) Destructive }A, A, interference occurs when whenever Al reaches the values Al (A) 977.m (B) 82.4m (C) 67.3m (D) 47.5m (E) 23.8m

You have been taken to the emergency room. To get a constant update on your vital signs, equipment is attached to you, including a pulse oximeter. The pulse oximeter shines two LEDs on your finger to test how much oxygen is in your blood. One LED transmits in infrared (921 nm) and one transmits in visible red (632 nm). What are the frequencies of these LEDs? Red: (Hz) Infared: (Hz)

A distant galaxy is simultaneously rotating and receding from the earth. As the drawing shows, the galactic center is receding from the earth at a relative speed of ug = 2.30 × 106 m/s. Relative to the center, the tangential speed is V₁ = 0.310 × 106 m/s for locations A and B, which are equidistant from the center. When the frequencies of the light coming from regions A and B are measured on earth, they are not the same and each is different from the emitted frequency of 9.296 × 10¹4 Hz. Find the measured frequency for the light from (a) region A and (b) region B. (Give your answer to 4 significant digits. Use 2.998 × 108 m/s as the speed of light.) (a) Number (b) Number i 9.21E14 9.23E14 יזע Galaxy Units Hz Units Hz ING Earth די. B

Light is prepared so that it is polarized at 15.4 degrees with an intensity of 0.553 W/m2. The light passes through a polarizer oriented to pass polarization at an angle of 65.2 degrees and then through a second polarizer oriented to pass polarization at 90.0 degrees. What is the intensity in W/m2 of the light after passing through the second polarizer? (Enter answer with 3 digits right of the decimal.