14. Babies are naturally more sensitive to some pitched sounds differently than adults. This is due to the difference in the length of the ear canal. Calculate the fundamental resonant frequency f1 of the 1.27 cm long ear canal of a baby. Calculate the fundamental resonant frequency f2 of the 2.6 cm long ear canal of an adult. The answer is written in the form (f1, f2). The speed of sound in air is 344 m/s. (A) (7343 Hz, 4370 Hz) (B) (3543 Hz, 6880 Hz) (C) (6771 Hz, 3307 Hz) (D) (3443 Hz, 7698 Hz) (E) (9371 Hz, 5890 Hz)

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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