51. During ventricular fibrillation, the myocardial cells do not stop beating; instead, they fall into a state of extreme chaos and rapid twitching, which the heart cannot pump blood effectively. An Automated External Defibrillator (AED) acts to reboot the heart by forcing a powerful electric current through it. The AED must generate high voltage to deliver a current of approximately 20 Amperes into the body within a short duration of about 0.01 seconds. The energy setting for a modern AED is 300 Joules. Estimate the voltage V required for this device and the average chest wall impedance R during a shock. Assuming all processes satisfy Ohm's Law. (A) 2100 Volt, 105 Ohm (B) 1900 Volt, 90 Ohm (C) 1700 Volt, 85 Ohm (D) 1500 Volt, 75 Ohm (E) 1300 Volt, 65 Ohm

60. Positron Emission Tomography is a highly advanced imaging technology in modern medicine. PET is primarily used to observe cellular metabolism; this is especially useful for cancer. After the isotope in the radiopharmaceutical enters the body, it migrates to the lesion site and emits a positron. As the positron moves through the tissue, it strikes an electron within the body. When the two collide, annihilation occurs, converting matter into energy and emitting two gamma rays of equal energy. The detectors then use these two rays to calculate the precise location of the lesion. Assume that both the electron and the positron carry a kinetic energy K=0.23m0c2, where m0 is the rest mass of an electron and c is the speed of light. What is the wavelength of the gamma rays produced after a head-on collision? [Compton wavelength is λ0=h/(m0c), where h is Planck's constant] (A) λ = 2.83 λ0 (B) λ = 1.62 λ0 (C) λ = 0.81 λ0 (D) λ = 0.40 λ0 (E) λ = 0.25 λ0

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