Operators in a research lab utilize radiation material as part of their experiments. The radiation level XR in the lab is detected by a device that generates a signal VR that is proportional to XR. VR is fed to a peak detector circuit shown below, where D is an ideal diode (OV drop). At no time should XR (and accordingly VR) exceed a certain safe level denoted by VRmax = 6.0 V. If it does, the detector trips a comparator circuit that turns a blinking red light on. The signal VR is illustrated below, as well as the signal Vo at output of the detector. a) At what time does the radiation level exceed XRmax? b) At time 14:00, an operator adds a shunt resistor across the output of the detector to turn off the blinking light. The light turns off after 10 seconds. What is the value of the resistance R? A 8 7. 6 5. 4 3 1012N inn -1 -2- -3 VR(V) -4 -5 VR D 5:00 6:00 7:00 8:00 K C 10 F VO Vp = 0.V 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 t (hour)