An ultrasonic sonar sensor is used to determine the distance between a robot and an object. Given that the speed of sound is 343 meters/second and the distance between the robot and the object is 250 centimeters (250 × 10–2 meters), find the round trip time for the sound wave to travel from the emitter to the object and back to the detector.

How can the noise level of a photomultiplier detector be reduced below the level of shot noise? a. It can't b. Use a solid-state detector instead of a vacuum photomultiplier c. Cool the detector using liquid nitrogen d. Use a double-beam instrument for background subtraction

18.a. How does dispersion affect light pulses in an optical fiber? A. It causes total internal reflection. B. It can cause pulses to be indistinguishable. C. It causes pulses to die off as they travel down a fiber. D. It causes pulses to increase in power as they travel down a fiber. 18.b. Which of the following frequency bands do single-mode optical fibers use for communication? A. L B. C C. S 18.c. What type of cable is presently used to route phone and internet service to homes? A. Patch B. Fiber optic C. Twisted copper D. Coaxial

For an electromagnetic system, what will be the return loss if the reflection coefficient is 0.5?