Name___________________ Wave Properties Period____ Introduction: The wave characteristics you will observe at this time are common to all waves. There are not separate characteristics for sound waves, light waves, water waves or any other kind of waves. In general, all waves follow the same rules. Because this is so, you can investigate waves in a coiled spring to learn about waves in general. Objective: During this investigation you will observe and record your observation of some basic wave characteristics. Equipment: Coil spring Slinky Stopwatch Procedure: Record your observations in the spaces provided in the Data and Observation section of this lab. A. Transverses and Longitudinal Waves: 1. Have your lab partner hold one end of the spring and stretch it along a smooth floor until it is about 5m long. Send a single pulse along its length (Note: several pulses together will form a transverse wave train). 2. Reach a short distance down the spring’s length and gather the coils toward you and then quickly release them. The pulse that travels along the spring is a longitudinal pulse. B. The Speed of All Wave of the same kind in a given medium: 1. Generate a transverse pulse in the coil. Measure the time it takes the pulse to travel down the medium. Calculate the speed of the pulse in the medium. Generate a second pulse which is larger than the first pulse. Measure its time to travel down the medium. Calculate the speed of the larger pulse. Compare the speeds of the pulses. Groups of pulses form waves. Shake the spring back and forth to generate waves of different amplitudes and frequencies. Compare the speeds of waves. C. Wavelength and Frequency: 1. Shake the spring back and forth rapidly to generate a wave train in the spring. The wavelength of that wave in the spring is the distance from crest to crest. The frequency of the wave is the same as the frequency at which you shake the spring. a. Shake the spring at a constant rate but slowly and then at a constant rate but quickly. Observe the wavelengths of both waves. D. The Interference of Waves: 1. Have your partner grasp one end of the spring while you grasp the other end. Practice sending pulses toward each other at the same time. Once practiced: a. Each of you send a single pulse of the same size down the spring on the same side of the spring. Observe what happens when the two pulses travel through each other. b. Each of you send a single pulse of different sizes down the spring on the same side of the spring. Observe what happens when the two pulses travel through each other. c. Each of you send a single pulse of the same size down the spring on the opposite sides of the spring. Observe what happens when the two pulses travel through each other. d. Each of you send a single pulse of different sizes down the spring on the opposite sides of the spring. Observe what happens when the two pulses travel through each other. E. Reflected Waves 1. Have your partner hold one end of the spring very firmly. Send a transverse pulse to the rigid end and observe the phase of the reflected pulse. 2. Now tie a long piece of string to the spring. Have your partner hold the string while you send a pulse towards the end supported by the string. (The string represents a less rigid medium than the initial wave in the spring). Observe the phase of the reflected pulse. F. Wave Transfer from One Medium to Another: 1. Connect the spring to a slinky (two different mediums). With your partner stretch the spring and slinky. Send a wave train down the spring. Observe their behavior at the boundary between the two springs. The wavelength in each medium and the frequency in each medium. 2. Connect the spring to a slinky (two different mediums). With your partner stretch the spring and slinky. Have your partner send a pulse down the slinky. Observe their behavior at the boundary between the two springs. Observe how the reflected and transmitted wave changes as it passes from one medium into the other. Data and Observations: A. Transverse and Longitudinal Waves 1. Compare the direction of particle motion to the direction of wave travel in a transverse wave. _____________________________________________________________ _____________________________________________________________ 2. Compare the direction of particle motion to the direction of wave motion in a longitudinal wave. _____________________________________________________________ _____________________________________________________________ B. The Speed of All Wave of the same kind in a given medium: 3. Describe the speeds of pulses of different amplitudes in a given medium. _____________________________________________________________ _____________________________________________________________ 4. Compare the speeds of waves of different frequencies in a given medium. _____________________________________________________________ _____________________________________________________________ C. Wavelength and Frequency: 5. Compare the wavelengths of waves with higher frequencies with the wavelengths of wavelengths of waves with lower frequencies. _____________________________________________________________ _____________________________________________________________ D. The Interference of Waves: 6. Describe the magnitude of amplitude when two pulses in phase meet in the spring. _____________________________________________________________ _____________________________________________________________ 7. Describe what happens when two pulses of equal amplitude and 180o out of phase meet in the spring. _____________________________________________________________ _____________________________________________________________ 8. What happens if the two pulses are in phase? _____________________________________________________________ _____________________________________________________________ 9. Describe the pulses after the pass through each other. _____________________________________________________________ _____________________________________________________________ 10. Draw the superposition of waves A & B as they pass through each other. A B --------------------------------------------------------------------------------------------------- A B --------------------------------------------------------------------------------------------------- E. Reflected Waves 12. How does reflection of a wave from a rigid barrier affect its phase? _____________________________________________________________ _____________________________________________________________ 13. Reflection of a pulse from a less rigid medium has what affect on its phase? _____________________________________________________________ _____________________________________________________________ F. Wave Transferal from One Medium to Another: 14. Describe what happens to a wave when it reaches the boundary between the two springs. _____________________________________________________________ _____________________________________________________________ 15. From your observation of one medium change. What do you think might happen to the speed of a wave when it enters a new medium? _____________________________________________________________ _____________________________________________________________ 16. What happens to the wavelength of a wave when it enters a new medium? _____________________________________________________________ _____________________________________________________________ 17. What happens to its frequency? _____________________________________________________________ _____________________________________________________________ Questions: For questions 1-4, sketch the results of wave A and B a) When they meet. b) When the pass 1. B A a) b) A 2. B a) b) 3. A B a) b) 4. A B a. b.