3. Strike a tuning fork and move it in a wide circle around your head. Listen for the pitch of the sound. ANSWER ON YOUR DOCUMENT

Transcription

1 STATION 1 TUNING FORK FUN Do not hit the tuning forks on the table!! You must use the rubber mallet each time. 1. Notice that there are two strings connected to the tuning fork. Loop one end of each string around your fingers, one string per hand, and place your fingers in your ears. Have your partner TAP the tuning fork with the mallet (make sure it stays hanging). 2. Strike a tuning fork and bring the tines (forks) 2-3 cm from you ear. Slowly rotate the tuning fork in a complete circle. Carefully describe the changes in the amplitude (loudness) of sound and draw the tuning fork in its loudest position and its quietest position. ANSWER ON YOUR DOCUMENT 3. Strike a tuning fork and move it in a wide circle around your head. Listen for the pitch of the sound. ANSWER ON YOUR DOCUMENT 4. Strike the tuning fork and note the pitch of the sound. Its frequency should be labeled on the fork. While holding another tuning fork of the same frequency, strike the first fork and hold it (without touching) near the second tuning fork. After a few seconds, stop the vibrations of the first tuning fork and hold the second one to your ear. ANSWER ON YOUR DOCUMENT 5. Strike the tuning fork and hold it against an Aluminum ball on a string. ANSWER ON YOUR DOCUMENT STATION 1 TUNING FORK FUN Identify what wave behavior you observed using the terms listed below. Give a brief explanation why. INTERFERENCE DOPPLER REFLECTION RESONANCE REFRACTION Resonance and Refraction Write A for examples of resonance, B for examples of refraction and C for neither. A singer shattering a glass with their voice. The Tacoma narrows bridge collapsing. The bent appearance of objects in water. Pumping your legs on a playground swing. Noise canceling headphones. Appearance of rainbows from a prism. Double bouncing on a trampoline. The sound of the sea in a sea shell.

2 Station 2: Wave Interference Read through the provided material define the required words on your answer sheet. Look through the numbered cards sort them into either constructive or destructive interference. Wave interference is the phenomenon that occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium. Constructive interference is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the same direction. Destructive interference is a type of interference that occurs at any location along the medium where the two interfering waves have a displacement in the opposite direction.

3 This type of interference occurs when one waves crest meets another waves trough. Station 2 Wave Interference Indicate which waves will result in constructive interference and which will result in destructive interference. 1. Define constructive interference and give an example 2. Define destructive interference and give an example. Sort the statements and pictures and write the NUMBER in the correct box below. Constructive Destructive

4 Station 3: Vocabulary Match the terms to the correct explanation write the # of the explanation in the corresponding box on your answer sheet. A. The time it takes for a wave to complete one complete cycle. B. A measure of a waves energy. C. The source of all waves. D. A sound wave is an example. E. An electromagnetic wave is an example. F. The number of waves that pass in a given time (normally 1 second.) G. Is inversely proportional to frequency. As it increases, frequency decreases. H. When you squeeze together the coils of a spring and then release them, you are creating this type of wave. I. Rays from the sun are an example. J. Usually measured from crest to crest or trough to trough. K. Inversely proportional to wavelength. L. A weight on the end of a spring bobs up and down one complete cycle every 5 seconds. This is the weights. M. Measured in hertz. N. Measured in meters, centimeters or nanometers. Station 3 Vocabulary Match the terms to the correct explanation write the # of the explanation below. Period Frequency Compressional Transverse Vibration Amplitude Wavelength STATION 4: COMPARING WAVES Use the waves pictured to answer the questions on your sheet DO NOT HAVE AN ELECTRONIC COPY OF THESE STATION 5: INSTRUMENTS Rubber Band Guitar Create a rubber band guitar out of the rubber bands and box provided. Experiment with the sounds produced by rubber bands of different thicknesses and tensions. Vibrating Ruler Let half of the ruler hang over the counter. Bend (slightly) the ruler over the end of the counter. Let it go. Watch the movement of the ruler. Try changing the length of the ruler that is left on the table and listen to the difference. Straw Obo Take a straw and cut one end to a point as in the picture to the right. Practice blowing it until you hear a consistent buzzing sound. Use the scissors and while blowing through the straw have a partner carefully cut an inch or so off the bottom of your straw obo. Listen to how the sound changes. Have your partner use the scissors again and continue to cut an inch of the bottom at

5 the time, while blowing through the straw and listen to the change in the sound. THROW YOUR STRAW AWAY WHEN YOU HAVE FINISHED. STATION 5 Rubberband guitar 1. How does tension relate to the pitch heard? 2. How does the thickness of the rubber band relate to the pitch heard? 3. Describe relationship of frequency in a string to tension, length, and diameter. 4. What is vibrating to create the sound? 5. Why must the rubber bands been put on to the box to be heard? Ruler 1. How does the pitch change as the portion of the ruler that is off the table changes? 2. How does the frequency change as the portion of the ruler that is off the table changes? Straw obo 1. How did the pitch change as the straw obo got shorter? 2. What type of wave is produced within the straw? STATION 6 CALCULATIONS 1. What is the speed of sound at 28 C? 2. One wave hits the shore every 3 seconds. What is it s frequency? If its speed is 2.5 m/s What is the wavelength of the wave? 3. A sound in air has a frequency of 326 Hz. What is its wavelength? 4. An ambulance travels at 16 m/s. Its siren emits a sound with a frequency of 400Hz. A. What frequency is heard by the passenger of a car approaching the ambulance at a rate of 20 m/s? B. What is the frequency heard by the passenger of a car as she passes and moves away from the ambulance?

6 STATION 7 STANDING WAVES At certain frequencies the vibrating string will form wave patterns like those shown in the picture. Each of the patterns occurs at a resonance of the string. The resonances are called harmonics and they are described by the number of bumps seen on the vibrating string. The wavelength of each harmonic is the length of one complete wave. One complete wave is two bumps. Therefore, the wavelength is the length of two bumps. The string is 1 meter long. If you have a pattern of three bumps, the wavelength is 2/3 meter, since three bumps equal 1 meter and a whole wave is two of the three bumps. Finding the standing waves You noticed that the standing waves only occur at certainspecial frequencies. The wiggler applies a periodic force to the string. When the periodic force matches the natural frequency of the string, a large response develops (resonance). 1.Use the frequency control to find the first through the eighth harmonics of the string(at least). 2. Record the frequency and wavelength for each harmonic in Table 1. You should fine- tune the frequency to get the largest amplitude wave before recording the data. Look for harmonics 2 to 6 before looking for the first one. The first harmonic, also called the fundamental, is hard to find with exactness. Once you have the frequencies for the others, they provide a clue for finding the frequency of the first harmonic. Station 7 Standing Waves 1. What are the resonances called? 2. One complete wave is bumps. Those bumps are called? Harmonic # Frequency (Hz) Wavelength (m) Frequency times wavelength

7