(A)Music. When a person sings, his or her vocal cords vibrate in a repetitive pa
ID: 2109331 • Letter: #
Question
(A)Music. When a person sings, his or her vocal cords vibrate in a repetitive pattern having the same frequency of the note that is sung. If someone sings the note B flat that has a frequency of 466Hz, how much time does it take the person's vocal cords to vibrate through one complete cycle, and what is the angular frequency of the cords?(B)Hearing. When sound waves strike the eardrum, this membrane vibrates with the same frequency as the sound. The highest pitch that typical humans can hear has a period of 50.0mu s . What are the frequency and angular frequency of the vibrating eardrum for this sound?
(C)Vision. When light having vibrations with angular frequency ranging from 2.7x10^15 rad/s to 4.7x10^15 rad/s strikes the retina of the eye, it stimulates the receptor cells there and is perceived as visible light. What are the limits of the period of this light?
(D)When light having vibrations with angular frequency ranging from 2.7x10^15 rad/s to 4.7x10^15 rad/s strikes the retina of the eye, it stimulates the receptor cells there and is perceived as visible light. What are the limits of the frequency of this light?
(E)Ultrasound. High-frequency sound waves (ultrasound) are used to probe the interior of the body, much as x rays do. To detect a small objects such as tumors, a frequency of around 5.50 MHz is used. What are the period and angular frequency of the molecular vibrations caused by this pulse of sound?
Explanation / Answer
Your approach looks OK to me, but your significant figures are a bit out of whack. Your data has three significant figures, and with the calculations you're doing, your results should have three as well. So T = 0.00215 s and ? = 2930 rad/s If it was a computer, rather than a human being, saying that you are incorrect, too few significant figures can often be a problem. b)f = 1/T = 1/50µs = 1/50x10^-6 = 20000Hz converting to rad/s we get 20000*2*p = 1.26x10^5 rad/s b) T = 1/f = 2p/? = 2p/2.7x10^15 = 2.33x10^-15s and T = 1/f = 2p/? = 2p/4.7x10^15 = 1.34x10^-15s so 1.34x10^-15,2.33x10^-15 c) f = ?/2p = 2.7x10^15/2p = 4.30x10^14Hz f = ?/2p = 4.7x10^15/2p = 7.48x10^14Hz so 4.3x10^14,7.5x10^14 e) T = 1/f = 1/5.2x10^6 = 1.92x10^-7s ? = 2pf = 2p*5.20x10^6 = 3.27x10^7 rad/s 1.92x10^-7,3.27x10^7
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