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# hw37 - Muraj Hamza Homework 37 Due May 7 2006 11:00 pm Inst...

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Muraj, Hamza – Homework 37 – Due: May 7 2006, 11:00 pm – Inst: Florin 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Sound in air can best be described as which of the following type of wave? 1. Electromagnetic 2. Polarized 3. Longitudinal correct 4. Torsional 5. Transverse Explanation: A sound wave in the air is propagated by the oscillation of air molecules. It is best described as longitudinal wave. 002 (part 1 of 1) 10 points A bat can detect small objects such as an insect whose size is approximately equal to one wavelength of the sound the bat makes. If bats emit a chirp at a frequency of 68 . 9 kHz, and if the speed of sound in air is 349 m / s, what is the smallest insect a bat can detect? Correct answer: 5 . 06531 mm. Explanation: From λ = v f , we get λ = (349 m / s) (68900 Hz) = 5 . 06531 mm . 003 (part 1 of 1) 10 points The sound emitted by bats has a wavelength of 3 . 52 mm. What is the frequency in air? Correct answer: 97443 . 2 Hz. Explanation: v = f λ so f = v λ Dimensional analysis of f : m s ÷ mm = m s · 1 mm · 1000 mm 1 m = 1000 s = 1000 Hz 004 (part 1 of 1) 10 points Why is an echo weaker than the original sound? 1. The echo has a longer wavelength than the original sound due to the reflection. 2. The echo has a smaller amplitude than the original sound because sound spreads and its intensity decreases with distance. correct 3. The echo has a shorter wavelength than the original sound due to the reflection. 4. The echo has a higher frequency than the original sound due to the reflection.

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hw37 - Muraj Hamza Homework 37 Due May 7 2006 11:00 pm Inst...

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