Grace+Carroll+4-15-09

On April 15, 2009 I observed Mr. Manning’s 4th period Physics class again. The class started with a daily question that related to transverse and longitudinal waves. Transverse waves can be ocean waves, and kind of resemble a series of hills. Longitudinal waves can be sound waves, and may resemble coils. They are also composed of a series of compressions and rarefactions. The daily question will be illustrated in the visual accompanying this report. We had to predict which direction a point on a longitudinal and transverse wave would travel, according to the picture. On the longitudinal wave, the point moved to the right, because of the compressions and rarefactions. On the transverse wave, the point moved up and then down, which was easy for me to understand because the wave resembled a hill, and when something goes up a hill, it has to come down. After completing the daily question, the students reviewed a worksheet they had been working on the previous day, which was on pages 2 and 3. The worksheet contained information about waves, including how they move and the different types of waves, which I will explain in this article. Energy can be transferred through two different ways, which is through moving mass and waves. Waves are caused by pulses, which are disturbances of masses that cause a change in movement. Three types of waves that we learned about were mechanical waves (which are produced in sounds and slinkies), electromagnetic waves (which are produced in light) and matter waves which have to do with subatomic particles. Electromagnetic waves don’t need a medium, and a medium is an object which is used to help transfer energy. The class also learned the three types of mechanical waves which are transverse, longitudinal and surface. Surface waves are simply a combination of transverse and longitudinal waves. In each wave, there is frequency, period and amplitude. Frequency is the number of cycles a wave makes per second and is measured in Hertz. Period is the time it takes for one wave to pass a point and is measured in T’s. Amplitude is the distance from the center or equilibrium line to the crest or trough. The crest is the highest point of a wave, while the trough is the lowest point. The class also learned that the period or time it takes to make a wave decreases when the frequency increases because the waves would be smaller so it would take less time to hit the person. One can change the frequency of waves by using a lighter or heavier medium. After the students reviewed the worksheet, they were handed a packet (pages 4-6). The packet was the Mechanical Wave Characteristics Lab and first the students had to make predictions. One of the predictions was to determine what factors can change the speed of a mechanical wave pulse on a spring. My predictions were that the length of the spring would not change the speed; neither would the amplitude of the wave pulse. But I did think that the frequency of the wave pulse would change the speed, as well as the type of spring used. Another prediction I made was that the greater the frequency is, the greater the wavelength would be. I also predicted that a longitudinal wave pulse and a transverse wave pulse on the same medium travel at equal speeds. The class was divided into groups, and each group tested each prediction. The group I was in tested how long a longitudinal wave and transverse wave travel, and tested this by using a spring. One member of the group would hold one end of the spring, and another member would hold the other end. The two people created either transverse or longitudinal waves by moving the spring a certain way, and I recorded the amount of time it took. Unfortunately, the period ended before we could finish our experiment, but hopefully tomorrow the students will be able to finish it and compare the results with the rest of the class. I thought the day was very interesting, and enjoyed classifying different types of waves. I’m looking forward to my next visit with this class!