1. Ultrasonic waves have many applications in technology and medicine. One advantage is that large intensities can be used without danger to the ear. Cite another advantage of their short wavelength. (Hint: Why do microscopists use blue light rather than white light to see detail?)
2. If the distance from a bugle is tripled, by what factor does the sound intensity decrease? Assume that no reflections afffect the sound.
3. A rule of thumb for estimating the distance in kilometers between an observer and a lightning stroke is to divide the number of seconds in the interval between the flash and the sound by 3. Is this rule correct? Defend your answer.
4. Why will marches at the end of a long parade following a band be out of step with marchers near the front?
2006-12-08 13:02:14 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Well, here's an answer for #1. If an object is smaller than a wave's wavelength, then the wave will simply defract around the object, instead of reflecting off of it (reflection allows you to see objects). This is why objects smaller than the wavelength of visible light do not have color and cannot be seen with light microscopes.
So, the small wavelength of ultrasonic waves means that they can reflect off of very small objects, allowing us to see them.
2006-12-08 13:42:17 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Here's an answer to #2. Picture an imaginary bubble with radius of 1 meter centered on the bugle. Then paint a square on the surface of the bubble. Imagine a 2nd bubble with radius of 3 meters centered on the bugle. Imagine sound from the bugle reaching the square on the inner bubble. Now picture this sound continuing on to the 2nd bubble. The sound that passed through the first square now reaches a square on the 2nd bubble. The sides on the 2nd square are 3 times as long, so the area is 9 times as much. The sound intensity at the 2nd bubble is 1/9th as high.
2006-12-08 22:09:15 · answer #2 · answered by sojsail 7 · 0⤊ 0⤋
3. Speed of sound is 345m/s. This means that travels 1035m every 3 seconds, or roughly 1km every 3 seconds. Speed of light is 1 million times faster, so it can be considered that when you see the lightning the sound starts traveling, and dividing the time in seconds by 3, you get the distance in km.
4. In a long parade (say 100m) the people at the back will be hearing the music 0.3 s later than the people at the front (closer to the band), and therefore they will be out of step by 0.3s
2006-12-08 22:05:28 · answer #3 · answered by Eng_helper 2 · 0⤊ 0⤋